LIBRARY 

OF   THE 

UNIVERSITY  OF  CALIFORNIA. 


. 


Class 


H 


Development 


AND 


Electrical    Distribution 
of  Water  Power 


BY 

LAMAR  LYNDON 


FIRST  EDITION 
FIRST  THOUSAND 


NEW    YORK: 

JOHN    WILEY   &   SONS 

LONDON  :  CHAPMAN   &  HALL,   LIMITED 
1908 


fc 


GENERAL 


Copyright,  ryoS, 

BY 

LAMAR  LYNDON 


PRESS   OF    THE    PUBLISHERS     PRINTING    COMPANY,    NEW   YORK 


PREFACE. 

IT  is  to  be  understood  that  this  work  is  not  a  text-book  on 
electricity,  hydraulics,  concrete  work,  nor  construction  engineering. 
The  purpose  has  been  to  produce  a  purely  engineering  treatise 
in  which  all  the  salient  facts  concerning  the  hydraulic  development 
of  power,  its  conversion  into  electrical  energy,  and  its  transmission 
over  long  distances,  are  collated,  and  their  interdependence  showrn. 

With  but  few  exceptions,  no  basic  principles  of  electricity  are 
set  forth  nor  are  the  derivations  given  of  the  formulae  used. 

With  the  many  excellent  works  on  hydraulics  and  electricity 
now  published,  it  is  needless  to  reproduce  their  contents  here. 
It  is  with  the  relationships  between  the  available  power,  methods 
of  development,  the  machinery  and  apparatus  employed,  and 
the  final  use  to  which  the  energy  will  be  put,  that  this  book  is  con- 
cerned. It  is  to  be  noted  that  the  use  of  mathematics  has  been 
studiously  avoided  and  the  text  may  be  followed  understanding!}- 
by  any  one  having  an  elementary  knowledge  of  algebra. 

The  descriptions  of  plants,  taken  from  prominent  technical 
periodicals,  is  believed  to  be  a  valuable  addition  and  innovation, 
both  in  that  the  principles  set  forth  in  the  main  body  of  the  book 
are  here  shown  in  concrete  form,  practically  applied,  and  that  they 
constitute  an  aggregated  expression  of  the  broad  ideas  held  on 
this  subject  by  that  portion  of  the  engineering  profession  ex- 
perienced in  this  class  of  work. 

The  author  has  found,  in  his  own  practice,  that  the  best  way 
to  investigate  a  problem  is  to  discover  all  that  has  been  done  in 

iii 

1 7.347:5 


iv  PREFACE 

the  same  field  by  engineers  of  ability,  and  take  this  combined  knowl- 
edge and  experience  as  the  starting  point.  Such  a  method, 
however,  involves  considerable  work  and  loss  of  time  in  searching 
through  the  files  of  the  technical  journals.  Assembled  here, 
after  selection  from  among  a  large  number,  it  is  believed  that  the 
ease  with  which  these  examples  may  be  referred  to  justifies  their 
reprinting  and  enhances  the  usefulness  of  this  book. 

The  author  wishes  here  to  express  his  appreciation  of  the 
courtesy  extended  by  the  editors  of  The  Electrical  World,  The 
Electrical  Review,  The  Engineering  Record,  and  The  Engineering 
News,  who  have  kindly  permitted  the  use  of  abstracts  of  descrip- 
tions of  plants  from  their  respective  periodicals. 

LAMAR  LYNDON. 

NEW  YORK,  October,  1907. 


CONTENTS 


Part    I 
HYDRAULIC   DEVELOPMENT 

CHAPTER  PAGE 

I.  GENERAL  CONDITIONS, i 

II.  DAMS,                                                                             .         .  16 

III.  CANALS  AND  FLUMES, 32 

IV.  DESIGN  OF  HYDRO-ELECTRIC  POWER-HOUSES,           .         .  38 
V.  WATER-WHEELS, 51 


Part  II 
ELECTRICAL   EQUIPMENT 

VI.  GENERAL  CONSIDERATIONS, 71 

VII.  ALTERNATING-CURRENT  DYNAMOS    ....         -76 

VIII.  TRANSFORMERS, 92 

IX.  TRANSMISSION  CONDUCTORS,  ....  .100 

X.  POLE  LINE  AND  ACCESSORIES,         .         .         .  .120 

XI.  LIGHTNING  PROTECTION,         ....  135 

XII.  SWITCHING  AND  CONTROLLING  APPARATUS,      .         .  141 

APPENDIX 

COMPUTATION  OF  PRESSURES  SET  UP  IN  WATER  PIPES     .   152 


VI  CONTENTS 


Part   III 

DESCRIPTIONS   OF  HYDRO-ELECTRIC  GENERATING 
AND    TRANSMISSION  PLANTS 

PAGE 

1.  TOFWEHULT-WESTERWIK  PLANT   IN   SWEDEN,       .         .         -157 

2.  HYDRAULIC  DEVELOPMENT  AT  WEST  BUXTON,  ME.,     .         .   164 

3.  HYDRAULIC  POWER  DEVELOPMENT   OF   THE  ANIMAS    POWER 

AND  WATER  Co.  AT  DURANGO,  C£L 176 

4.  HYDRO-ELECTRIC  PLANT  OF  THE  CITY  OF  DRAMMEN,  NORWAY,   183 

5.  GREAT    FALLS    STATION   OF    THE  SOUTHERN  POWER  Co.  IN 

N.  CAROLINA 193 

6.  THE  HYDRO-ELECTRIC   DEVELOPMENT    AT    TRENTON    FALLS, 

N.Y., .'         .  .  208 

7.  HYDRO-ELECTRIC  PLANT  OF  THE  McCALL  FERRY  POWER  Co.,  Pa.,  215 

8.  THE   TAYLOR'S  FALLS-MINNEAPOLIS  TRANSMISSION    SYSTEM, 

MINNESOTA, 229 

9.  THE   KERN    RIVER    PLANT    OF  THE  EDISON    ELECTRIC  Co., 

CALIFORNIA     .........  263 


OF  THE 

UNIVERSITY 


DEVELOPMENT  AND  ELECTRICAL  DISTRI- 
BUTION OF  WATER  POWER 


PART  I. 

CHAPTER  I. 

GENERAL    CONDITIONS. 

THE  most  important  factor  in  the  development  of  a  water 
power  is  to  determine,  in  advance,  the  actual  amount  of  power 
that  may  be  obtained  continuously  over  a  long  period  of  years. 
Failure  to  give  this  matter  the  attention  and  careful  investigation 
which  its  importance  deserves  has  resulted  in  financial  disaster 
in  many  instances.  Too  often,  engineers  survey  hydraulic  prop- 
erties, and  report  that  the  flow  of  water  is  a  given  quantity  per 
second,  and  therefore  the  power  obtainable  is  a  certain  amount. 
Such  computations  are  correct  jor  the  particular  day  on  which  the 
survey  is  made,  but  obviously  the  amount  of  water  flowing,  and, 
therefore,  the  power,  may  change  within  a  few  hours.  Laymen 
who  know  nothing  of  engineering  are  familiar  with  the  variation 
in  the  flow  of  streams  with  the  time  of  the  year,  and  in  some  years 
the  flow  is  less  or  greater  for  a  certain  season  than  it  normally 
is  at  the  same  period. 

At  times,  water-power  development  is  undertaken  on  the  basis 
of  the  ability  to  supply  a  given  amount  of  power  for  the  greater 
part  of  the  year,  and  a  less  amount  during  the  short  time  of  the 
dryest  season  or  when  the  stream  is  so  greatly  flooded  that  opera- 
tion of  water  wheels  is  impossible.  This  also  is  an  erroneous 
basis  on  which  to  determine  the  value  of  a  water  power  unless  there 
is  some  class  of  industry  to  which  the  power  may  be  sold,  which 


2  DEVELOPMENT   AND   DISTRIBUTION  OF   WATER   POWER 

can  use  intermittent  power  and  which  can  suffer  stoppage  or  re- 
duction of  its  operations  without  material  loss.  In  this  case,  if 
the  amount  of  power  to  be  taken  by  the  intermittent  power- users 
be  previously  known,  together  with  the  frequency  and  duration 
of  the  shut-downs  they  can  allow,  a  fairly  accurate  conclusion  as 
to  the  value  of  the  power  and  the  advisability  of  developing  it  may 
be  formed. 

Still  other  developments  are  made  having  auxiliary  steam 
plants,  which  are  used  to  help  out  the  water  power  when  the  stream 
flow  is  too  low  to  furnish  the  required  energy.  This  is  an  ad- 
mirable arrangement,  where  the  value  of  the  power  sold,  during 
the  several  months  when  water  in  plenty  is  available,  is  sufficient 
to  pay  the  cost  of  operating  with  the  assistance  of  steam,  during 
the  short  time  of  low  water.  Usually,  however,  the  proper  basis 
on  which  to  fix  the  amount  of  available  power  is  to  take  a  series 
of  records  of  stream  flow  during  the  times  of  maximum  and 
minimum  flow.  These  observations,  to  be  reliable,  should  ex- 
tend over  several  years,  or  over  one  year  which  is  admittedly 
the  dryest  known  in  a  number  of  years. 

In  the  United  States,  the  Government  has*ong  maintained  gauges 
at  different  points  on  most  of  the  large  rivers,  and  their  records 
are  available  and  may  be  used  in  computing  the  available  power 
without  making  any  additional  observations  on  the  stream  itself. 
In  many  countries,  however,  the  engineer  is  dependent  on  his  own 
observations,  and  as  these  cannot  be  carried  over  a  long  number 
of  years  he  must  fall  back  on  the  methods  of  computation  from 
the  rainfall,  the  drainage  of  the  stream,  the  local  conditions  as  to 
character  of  the  country,  its  vegetable  growths,  and  whether  its 
geological  formation  is  such  that  underground  storage  reservoirs 
exist  which  supply  springs  that  continue  to  feed  the  streams  dur- 
ing dry  weather.  With  these  data,  reinforced  by  experience,  a 
fairly  accurate  determination  of  the  minimum  stream  flow  may 
be  arrived  at. 

The  character  of  the  underbrush,  shrubbery  and  trees,  their 
extent;  the  proportion  of  wooded  area  to  that  denuded  of  trees, 


GENERAL   CONDITIONS  3 

the  proportion  under  cultivation,  all  have  a  marked  influence  on 
the  variation  in  the  flow.  Trees  and  shrubs  tend  to  hold  the 
rain  water  and  make  it  move  slowly  toward  the  stream — so  slowly 
that  much  of  it  is  absorbed  into  the  earth  and  then  reaches  the 
river  or  its  tributary  creeks  only  by  percolation  which  greatly 
retards  its  movement.  These  effects  combine  to  equalize  the 
amount  of  water  which  is  given  to  the  stream  by  each  rainfall. 
Rains  come  intermittently  and  are  of  varying  volume.  The  flow 
of  streams  would  be  equally  intermittent  and  variable  as  to  volume 
if  it  were  not  for  these  retarding  influences.  Cases  are  on  record 
where  water  powers,  which  were  at  one  time  good  and  satisfactory, 
have  been  injured  by  subsequent  cutting  away  of  timber  and 
underbrush  over  the  drainage  area  of  the  streams  supplying  them. 
These  power-plants  are  now  subjected  to  heavy  floods  in  the  wet 
season  of  the  year,  and  the  available  water  in  the  dry  season  is 
smaller  than  it  formerly  was.  Therefore,  this  factor  must  be  given 
due  consideration.  Where  springs  are  numerous,  they*  tend  to 
keep  the  stream  flow  up  in  dry  weather  and  these  are  valuable 
when  they  discharge  enough  water  to  be  of  real  assistance. 

The  character  of  the  industries  to  which  the  power  will  be 
transmitted  also  has  to  be  considered.  If  the  general  use  is  for 
lighting,  for  driving  cotton  mills,  factories,  and  the  like,  the  only 
power  tliat  can  be  counted  on  in  the  development  is  that  produced 
by  the  smallest  flow  oj  water  that  occurs  during  the  entire  year. 
Obviously,  if  an  amount  of  power,  greater  than  this  minimum 
flow  will  furnish,  be  sold  to  users,  a  time  will  come  when  some  or 
all  of  them  will  have  to  reduce  their  working  capacity,  and  this 
result  tends  to  prevent  consumers  making  satisfactory  contracts 
for  power  with  the  development  company. 

The  minimum  flow  sometimes  may  be  increased  by  means 
of  storage.  When  a  dam  is  built  across  a  stream  and  a  lake  of 
considerable  area  is  formed,  the  water  thus  accumulated  may  be 
partially  drawn  off  during  the  dry  season,  the  total  water  passed 
through  the  turbines  being  that  furnished  by  the  stream  plus  that 
of  drainage  from  the  lake.  In  some  cases,  when  the  power  is 


4  DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

used  only  ten  hours  per  day  and  the  storage  area  is  sufficiently 
great,  the  water  which  flows  during  the  night  is  accumulated  in 
the  lake,  and  on  the  following  day  the  water  available  for  power 
is  that  supplied  by  the  stream  flow  plus  that  impounded  during 
the  previous  night.  In  this  way,  the  power  furnished  by  a  given 
stream  may  be  nearly  doubled. 

For  the  purpose  of  forming  extensive  storage  lakes,  dams 
of  great  height  and  length  are  often  constructed,  where  a  small 
dam,  further  up  the  stream,  and  a  canal  or  flume  leading  to  the 
foot  of  the  falls,  costing  much  less,  would  serve  just  as  well,  if 
the  question  of  storage  were  not  involved. 

In  order  to  determine  the  value  of  a  water  power  and  whether 
or  not  the  investment  of  its  cost  of  development  is  warranted, 
the  following  data  must  be  obtained: 

(1)  Variation  in  quantity  of  stream  flow. 

(2)  Amount  of  power  (gross)  available  at  minimum  flow. 

(3)  Cost    of   hydraulic   development    (i.e.,    dam,    canal,    tail 
race,  forebay,  head-gates,  flumes,  overflowed  land,  riparian  rights). 

(4)  Cost  of  power  station  and  foundations. 

(5)  Cost  of  generating  equipment    (i.e.,    water-wheels,   gov- 
ernors,   generators      switchboard,    transformers,     miscellaneous 
equipment). 

(6)  Cost  of    transmission   line  (i.e.,   wire;   insulators,   poles; 
cross-arms;   braces,  lag  screws). 

(7)  Labor,  freight,  and  cost  of  erection  on  all  work  as  above. 

(8)  Cost  of  operation  per  annum. 

(9)  Price  at  which  power  may  be  easily  sold  in  the  localities 
reached  by  the  transmission  lines. 

(10)  Annual  profit. 

The  annual  profit  as  thus  computed  shows  whether  the  interest 
on  the  cost  is  sufficient  to  make  the  investment  a  good  one. 

It  is,  of  course,  assumed  that  there  is  a  market  for  the  power, 
or  that  the  conditions  justify  the  belief  that  cheap  power  will  build 
up  a  locality  and  bring  power  users  within  the  radius  of  distribu- 
tion of  the  projected  plant. 


GENERAL   CONDITIONS  5 

The  quantity  of  stream  flow  and  its  variation  are  arrived  at  in 
one  of  the  following  ways: 

(a)  From  observations  extending  over  a  number  of  years. 

(b)  From  records  of  rainfall  and  drainage  area  of  stream 
down  to  location  of  power  house. 

(c)  From  a  few  observations  made  at  the  time  of  known  low 
water. 

Where  possible,  all  of  these  means  should  be  used  to  check 
the  final  result. 

From  (a)  and  (b)  the  maximum  as  well  as  the  minimum  flows 
are  obtained,  and  either  is,  therefore,  preferable  to  (c)  alone. 
Neither  (b)  nor  (c)  alone  should  ever  be  accepted  as  final,  but 
the  two  always  used  together  to  check  each  other. 

The  maximum  flow  must  be  known,  so  that  the  dam  may  be 
designed  to  withstand  it,  and  the  spillway — that  is,  the  crest  of 
the  dam  over  which  the  water  flows — made  long  enough  to  allow 
the  maximum  volume  of  water  to  pass  over  it  without  an  excessive 
rise  in  the  height  of  the  water  over  the  dam. 

Abnormal  increase  in  the  height  of  water  above  the  spillway 
endangers  the  dam  and  may  result  in  its  being  swept  away. 

To  determine  the  flow  where  no  data  are  available,  it  is  cus- 
tomary to  proceed  as  follows: 

Select  two  points  along  the  stream  about  three  hundred  feet  apart. 
These  should  be  located  somewhere  along  the  stream  where  it  runs 
straight  without  curves,  bends,  falls,  or  eddy  whirls,  and  the  cur- 
rent is  down  the  middle  of  the  stream — not  near  either  bank. 
Make  a  cross-section  survey  of  the  stream  at  both  points,  and 
determine  the  area  of  each  section  in  square  feet.  Take  the 
average  of  these  two  sections — that  is,  add  the  areas  of  the  two 
sections  together  and  divide  their  sum  by  2.  This  gives  the  mean 
section.  At  times  of  high  and  of  low  water,  take  the  velocity 
of  the  stream  by  means  of  a  float  which  sinks  deeply  into  the 
water.  The  float  is  put  into  the  current  of  the  stream  about  four 
hundred  feet  above  the  upper  reference  point,  so  that  by  the  time 
it  has  been  carried  down  to  this  point  it  has  attained  the  velocity 


6  DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

of  the  stream.  Observe  accurately  the  time  required  for  the 
float  to  travel  from  the  upper  point  to  the  lower  one.  Knowing 
the  time  in  seconds  and  the  number  of  feet  the  two  points  are 
apart,  the  velocity  of  the  stream  flow,  at  the  times  these  obser- 
vations are  taken,  may  be  computed. 

The  average  velocity  of  the  stream  is,  however,  less  than  that 
of  the  main  stream  current,  and  it  is  customary  to  assume  the 
average  rate  of  flow  as  80  per  cent  of  that  of  the  float. 

The  number  of  cubic  feet  per  second  is  then  computed  by 
multiplying  the  average  cross-section  of  the  stream  by  the  average 
rate  of  flow. 

To  make  a  survey  of  the  cross-sections  of  the  stream  it  is  usual 
to  select  a  time  of  low  water  and  by  means  of  a  surveyor's  level 
take  the  differences  in  level  from  the  surface  of  the  water  out  to 
either  side  of  the  stream  to  such  a  distance  that  the  maximum 
high -water  point  is  reached,  care  being  taken  to  move  outward 
from  the  stream  at  right  angles  to  its  direction  of  flow.  Obser- 
vations are  made  at  intervals  of  from  two  to  twenty  feet,  depending 
on  the  variation  in  the  contour  of  the  banks,  and  the  distance  from 
the  water  surface  out  to  the  maximum  high- water  level. 

The  cross-section  of  the  stream  itself  is  then  determined.  The 
best  way  to  do  this  is  to  stretch  a  strong  iron  wire,  about  -^  of 
an  inch  in  diameter,  across  the  stream,  this  wire  having  been  pre- 
viously marked  by  small  metal  or  wooden  tags  spaced  along  it  at 
equal  intervals.  The  distance  apart  of  the  tags  should  be  not 
more  than  ten  per  cent,  of  the  width  of  the  stream.  With  a  steel 
tape,  weighted  at  one  end  by  a  heavy  plumb  bob,  measure  the 
depth  of  the  water  at  each  marking  on  the  transversely  stretched 
wire,  using  a  small  row-boat  when  necessary.  From  these  data 
the  cross- section  may  be  mapped  and  computed. 

This  is  done  by  assuming  some  scale  on  the  paper,  say  ^  of 
an  inch,  as  equal  to  one  foot  of  horizontal  distance,  and  some  other 
greater  scale,  say  one  inch,  as  equal  to  one  foot  of  vertical  measure- 
ment. 

Computing  the  area  of  the  cross-section  of  the  water  may 


GENERAL   CONDITIONS  7 

be  done  by  any  method  of  integrating  irregular  surfaces.  A  simple 
approximate  way  is  to  add  together  all  the  observed  depths  and 
divide  this  result  by  the  number  of  observations.  This  gives 
the  average  depth.  Multiply  this  average  depth  by  the  width  of 
the  stream,  in  feet,  and  the  product  will  equal  the  cross-section 
of  the  stream  in  square  feet. 

The  float  should  be  made  of  a  piece  of  wood  about  three  feet 
long  and  from  six  to  ten  inches  in  diameter.     Weights  should  be 


FIG.  i. 


fastened  to  one  end  of  the  piece  so  that  it  will  float  vertically, 
with  one  end  submerged  and  the  other  projecting  only  an  inch 
or  two  above  the  surface  of  the  water. 

In  order  to  observe  from  the  bank  the  position  of  the  float, 


8  DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

it  is  usual  to  fasten  a  small  piece  of  red  cloth  to  a  rod  or  piece 
of  wire  and  drive  this  rod  into  the  upper  end  of  the  float. 

The  distance  apart  of  the  two  points  selected  to  observe  the 
float  velocity  should  be  accurately  measured  and  stakes  driven 
in  the  ground  near  the  water's  edge,  to  fix  these  reference  points. 

The  foregoing  instructions  are  for  determining  the  flow  of 
moderate  and  large- sized  streams. 

In  measuring  small  streams  it  is  more  accurate  and  convenient 
to  construct  a  weir  dam  such  as  is  shown  in  Fig.  i.  This  is  made 
of  boards  as  is  indicated,  with  a  notch  B  extending  across  about 
two-thirds  the  width  of  the  stream  and  deep  enough  to  easily  pass 
all  the  water  through  it.  The  edges  of  the  notch  must  be  sharply 
bevelled  as  shown,  the  bevelling  being  on  the  down-stream  side. 

Ten  feet  up  the  stream  from  the  weir  dam  a  stake  E,  having 
a  smooth  upper  surface,  should  be  driven.  The  upper  face  of 
this  stake  must  be  exactly  at  the  same  level  as  the  lower  edge  of 
the  notch  B.  On  this  stake  the  depth  of  the  water  above  the 
edge  of  the  notch  must  be  measured.  Never  measure  this  depth 
at  the  notch. 

The  formula  for  determining  the  cubic  feet  per  second  of  flow  is : 

Q  =  3-33  X  (b  —  o.2h)  h  f  in  which 

Q  =  cubic  feet  per  second, 

b  =  length  of  the  notch  measured  in  feet, 

h= depth  of  water  over  notch  measured  in  feet. 

In  order  to  obviate  the  necessity  of  making  computations 
from  this  formula,  the  following  table  is  given,  which  shows  the 
cubic  feet  per  minute  with  various  depths  of  water  in  inches  over 
the  notch  for  each  inch  length  of  notch  up  to  depths  of  24!  inches. 

Column  No.  i  is  the  depth  in  inches  over  the  notch. 

Column  No.  2  is  the  flow  in  cubic  feet  per  minute  corresponding 
to  the  depth  as  given  in  column  i  for  each  inch  length  of  the  notch. 

Thus,  for  a  depth  of  10  inches  the  flow  is  12.71  cubic  feet 
per  minute  for  each  inch  length  of  notch.  Therefore  a  notch 
40  inches  wide  with  10  inches  depth  of  water  over  it  will  pass 
40  X  12.71  —  508.4  cubic  feet  per  minute. 


GENERAL   CONDITIONS  9 

TABLE  No.  i. — WEIR  TABLE — FLOW  FOR  EACH  INCH  IN  WIDTH. 


Inches 
Depth. 

X 

X 

3/*                    l/2 

X           X 

H 

Inches. 

I 

.40 

•47 

•55 

.65 

•74 

•83          -93 

1.03 

I 

2 

I.I4 

1.24 

1.36 

1.47 

i-59 

1.71         1.83 

1.96 

2 

3 

2.09 

2.23 

2.36 

2.50 

2.63 

2.78        2.92 

3-°7 

3 

4 

3.22 

3-37 

3-52 

3.68 

3-83 

3-99        4-i6 

4.32 

4 

5 

4-5° 

4.67 

4-84 

5-01 

5.18 

5-36        5-54 

5-72 

5 

6 

5-90 

6.09 

6.28 

6.47 

6.65 

6.85        7.05 

7-25 

6 

7 

7-44 

7-64 

7.84 

8.05 

8.25 

8.44        8.66 

8.86 

7 

8 

9.10 

9-3i 

9-52 

9-74        9-96 

10.18       10.40 

10.62 

8 

'  9 

10.86 

11.08 

11.31 

n-54 

11.77 

12.00          12.23 

12.47 

9 

10 

12.71 

'3-95 

13-19 

13-43 

!3-67 

13.93          I4.I6 

14.42 

10 

1  1 

14.67 

14.92 

15.18 

15-43 

!5-67 

15.96      16.20 

16.46 

ii 

12 

l6-73 

16.99 

17.26 

I7-52 

17.78 

18.05       l8-32 

18.58 

12 

13 

18.87 

19.14 

19.42 

19.69   !    19.97 

20.24      20.52 

20.80 

J3 

U 

21.09 

2i-37 

21.65 

21.94 

22.22 

22.51     22.79 

23.08 

14 

IS 

23-38 

23.67 

23-97 

24.26 

24.56 

24.86     25.16 

25.46 

15 

16 

25.76 

26.06 

26.36 

26.66 

26.97 

27.27     27.58 

27.89 

16 

17 

28.20 

28.51 

28.82 

29.14 

29-45 

29.76     30.08 

30-39 

17 

18 

30.70 

31.02 

31-34 

31.66 

31.98 

32.31  i  32.63 

32.96 

18 

iQ 

33-29 

33-61 

33-94 

34-27 

34.60 

34.94    35.27 

35-6o 

19 

20 

35-94 

36.27 

36.60 

36.94 

37-28 

37.62    37.96 

38-31 

20 

21 

38-65 

39.00 

39-34 

39-69 

40.04 

40.39     40.73 

41.09 

21 

22 

41-43 

41.78 

42.13 

42.49 

42.84 

43.20     43.56 

43-92 

22 

23 

44.28 

44.64 

45.00 

4S.38 

45-7  i 

46.08     46.43 

46.81 

23 

24 

47.18 

47-55 

47.91 

48.28 

48.65 

49.02  1  49.39 

49.76 

24 

If  the  depth  of  water  over  the  notch  is  not  an  exact  number 
of  inches,  column  3,  4,  5,  6,  7,  8,  or  9  must  be  used.  If  the  depth 
were  loj  inches,  the  flow  is  given  in  column  8,  and  on  the  same 
horizontal  line  as  the  figure  10  in  column  i ;  in  this  case  the  flow 
is  14.16  cubic  feet  per  minute  per  inch  length  of  notch.  Similarly, 
the  flow  per  inch  width  of  notch  may  be  found  by  taking  the  number 
out  of  the  table  from  the  column  headed  by  the  fraction  of  an  inch, 
and  opposite  to  the  even  number  of  inches  shown  by  the  depth 
measurement.  Multiply  the  figure  so  taken  by  the  width  of  the 
notch  in  feet,  and  the  result  is  the  cubic  feet  per  minute.  To  re- 
duce to  cubic  feet  per  second,  divide  the  feet  per  minute  by  60. 
Thus,  508.4  cubic  feet  per  minute  is  equal  to  a  flow  of  8.47  cubic 
feet  per  second. 

By  making  numerous  observations  at  different  seasons,  suf- 
ficient records  are  finally  obtained  to  settle,  fairly  well,  the  variation 


10          DEVELOPMENT   AND   DISTRIBUTION   OF    WATER    POWER 

in  stream  flow.  This  will  afterward  be  modified  by  the  available 
storage,  which  cannot  be  computed  until  the  height  of  the  fall  is 
determined. 

The  fall  is  found  by  starting  at  the  head  of  the  shoals  with  an 
engineer's  level,  the  lower  end  of  the  level  rod  being  against  the 
surface  of  the  water  for  the  first  observation.  The  second  obser- 
vation is  made  with  the  level  rod  on  the  bank  and  succeeding 
observations  are  made  with  the  level  rod  on  the  ground,  working 
down  to  the  foot  of  the  shoals.  When  this  point  is  reached  the 
last  observation  is  taken  with  the  end  of  the  rod  against  the  surface 
of  the  water,  and  thus  the  difference  in  level  between  the  head  and 
foot  of  the  shoals  is  determined. 

Generally,  the  rod  should  be  moved  over  to  the  water  at  inter- 
vals so  that  the  drop  at  various  points  may  be  taken  as  well  as  the 
total  difference  in  head.  Where  the  whole  drop  is  in  one  precipi- 
tous fall,  only  the  difference  in  level  between  the  top  and  bottom 
of  the  fall  is  obtainable  or  necessary. 

After  measuring  the  fall,  the  calculation  of  gross  available 
power  is  very  simple.  A  horse-power  (gross)  is  produced  when 
8.8  cubic  feet  per  second  flows  and  falls  a  distance  of  one  foot, 
or  if  one  cubic  foot  per  second  falls  a  distance  of  8.8  feet.  There- 
fore, to  find  the  power  of  a  given  fall,  multiply  the  cubic  feet  flow 
per  second  by  the  fall  in  feet  and  divide  the  product  thus  obtained 
by  8.8.  The  result  will  be  the  gross  horse-power  of  the  fall. 
For  instance,  take  a  fall  of  35  feet  and  a  flow  of  26  cubic  feet  per 
second:  35  X  26  =  210.  210  •*-  8. 8  =  103. 4  =  gross  H.P. 

Where  metric  measurements  are  used  these  figures  are  changed 
as  follows:  one  cubic  metre  of  water  per  second  falling  through 
one  metre  will  yield  13.2  H.P.  gross. 

For  example,  take  6  cubic  metres  of  water  per  second  falling 
through  12  metres.  The  product  of  6  by  12  =  72.  Multiplying 
this  by  13.2  the  result  gives  950  H.P. 

These  amounts,  however,  do  not  represent  the  power  that 
may  be  actually  utilized.  In  every  machine  or  motor  there  is 
some  loss.  The  loss  in  the  best  forms  of  water  wheels  is  about 


GENERAL   CONDITIONS  II 

20  per  cent,  of  the  gross;  so  that  the  net  power  available  at  the 
turbine  shaft  is  80  per  cent,  of  the  gross.  Thus,  if  the  calculated 
gross-power  is  100  horse-power,  the  amount  that  may  be  obtained 
at  the  turbine  shaft  is  80  H.P.  Having  determined  the  power  ob- 
tainable at  the  turbine  shaft  at  times  of  lowest  water,  if  this  is  ample 
for  all  possible  needs,  the  development  may  be  made  in  the  most 
inexpensive  manner  practicable  for  the  particular  conditions.  If, 
however,  the  power  is  insufficient  when  the  water  is  low,  it  becomes 
necessary  to  consider  the  question  of  storage. 

In  computing  the  available  volume  of  water  for  storage,  it 
must  be  remembered  that  the  level  of  the  reservoir  can  only  be 
lowered  a  comparatively  small  amount.  If  the  storage  lake  be 
drawn  off  too  much  and  its  level  sinks  too  far,  the  head  acting  on 
the  water-wheels  will  be  diminished  by  an  amount  that  will  impair 
the  operation  of  the  plant.  The  drop  in  level  of  the  reservoir  should 
never  exceed  thirty  per  cent,  of  the  effective  head.  In  cases  of  ex- 
treme necessity  this  drop  may  be  exceeded,  but  all  calculations  as  to 
the  amount  of  power  obtainable  from  a  given  stream  with  storage 
should  be  based  on  a  drop  in  head  not  exceeding  thirty  per  cent. 

The  amount  of  storage  is  more  often  regulated  by  financial 
considerations  than  engineering  possibilities.  A  concrete  ex- 
ample will  render  the  subject  clear. 

Consider  a  stream  220  feet  wide  having  a  fall  of  50  feet  in  a 
distance  of  3  miles.  There  are  three  methods  of  development 
possible.  One  is  to  cut  a  canal  from  the  head  of  the  shoals  to 
the  foot,  this  canal  running  level  along  the  hillsides,  and  construct 
a  small  deflecting  dam  at  the  head  of  the  shoals.  The  second  is 
to  build  a  dam  at  some  point  between  the  head  and  foot  of  the 
shoals,  and  run  a  canal  the  remaining  distance  to  the  foot  of  the 
shoals.  The  third  method  would  be  to  build  a  large  dam  at  the 
foot  of  the  shoals  and  dispense  with  the  canal. 

Assume  that  the  length  of  the  three  dams  would  be  the  same. 
Then  their  cost  would  be  approximately  as  follows — assuming 
that  the  base  of  each  dam  is  at  an  average  depth  of  10  feet  below 
surface  of  the  water: 


12          DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

First  dam  to  be  4  feet  above  water  surface,  making  a  total 
height  of  14  feet. 

Second  dam  to  be  placed  half-way  down  the  shoals  and  to  be  26 
feet  above  the  surface  of  the  water,  making  the  total  height  =1:36 
feet. 

Third  dam  to  be  placed  at  the  foot  of  the  shoals  and  to  be  51  feet 
above  the  surface  of  the  water,  making  a  total  height  of  61  feet. 

The  costs  are:  first  dam,  $5,500;  second  dam,  $35,000;  and 
third,  $90,000. 

The  cost  of  canal  to  carry  300  cu.  ft.  per  second  will  be  about 
$10,000  per  mile  if  cut  through  ordinary  clay  and  no  blasting 
is  necessary.  Adding  the  cost  of  canal  cutting  to  that  of  the  dam 
for  each  development,  the  total  costs  are — 

ist  development  $35,000  (dam  $5,000  +  3  miles  of  canal  at 
$10,000); 

2d  development  $50,000  (dam  $35,000  +  ij  miles  canal  at 
$10,000); 

3d  development  $90,000. 

Assume  the  selling  value  of  the  power  to  be  $15  per  annum 
for  lo-hour  power;  the  minimum  flow  is  160  cubic  feet  per  second, 
and  this  minimum  flow  lasts  for  28  days  in  extreme  dry  sea- 
sons. The  power  desired  is  that  furnished  by  300  cubic  feet  per 
second. 

With  the  first  development  at  the  lowest  cost  there  is  no  storage 
capacity.  In  the  second,  the  lake  formed  will  be  i|  miles  long 
and  will  have  an  average  width  of  possibly  350  feet.  This  latter 
is  determined  by  contours  which  are  run  at  the  time  of  surveying 
the  water  power,  and  the  figure  here  taken  is  only  an  assumption. 

The  area  of  this  lake  is  1.5  X  5,280  X  350  =  2,772,000  sq.  ft. 
The  depth  down  to  which  the  lake  may  be  drawn  is  10  feet  in 
this  case  (20  per  cent,  of  the  head).  The  total  water  available  for 
storage  is,  therefore,  2,772,000  X  10  =  27,720,000  cu.  ft. 

If  the  amount  is  drawn  off  in  28  days  the  draft  per  day  is 
990,000  cubic  feet  and  for  lo-hour  power  the  draft  per  second  is 
27.5  cubic  feet.  At  an  average  head  of  45  feet  and  80  per  cent. 


GENERAL   CONDITIONS  13 

efficiency    the    additional    power  obtained    from  storage  during 

the  dry  season  is  — ^  —  =^12  H.P.,  and   its    additional 

8.8 

cost  is  $15,000. 

This  is  over  $133  per  horse-power,  which  is  a  high  figure  for 
the  hydraulic  power  only  and  not  to  be  considered  in  localities 
where  the  yearly  rental  is  not  above  $15  per  horse-power. 

Consider  now  the  third  possible  development.  The  lake 
formed  by  its  dam  would  be  3  miles  long  and  (assumedly)  average 
450  feet  wide.  The  volume  of  storage,  with  10  feet  depth  of  draft, 
would  be  10  X  3  X  5,280  X  450-71,180,000.  The  draft  per 
second,  if  28  days  be  allowed  for  the  total  storage  discharge,  is  70.6 
cubic  feet,  which  at  an  average  head  of  45  feet  equals  300  horse- 
power additional,  derived  from  storage.  Its  additional  cost  is 
$90,000  —  $3 5,000 -=$5 5,000,  or  $183.00  per  horse-power,  which 
is  an  excessive  cost.  Therefore  in  this  case  it  would  be  best,  from 
a  financial  standpoint,  to  develop  with  the  small  dam  and  long  canal. 
Certain  conditions  might  alter  this  conclusion.  If,  for  instance, 
the  stream  flows  through  flat  country,  and  the  lake,  formed  by  the 
lower  dam,  were  extremely  wide,  so  that  the  amount  of  storage 
would  be  greatly  in  excess  of  the  above  figures,  the  cost  per  horse- 
power would  be  correspondingly  reduced,  and  one  of  the  higher 
cost  developments  would  be  the  advisable  one.  Also,  if  the  ex- 
treme low  water  during  the  dry  season  should  last  only  14  days, 
the  draft  per  second,  and  the  resulting  power,  would  be  increased 
in  the  ratio  of  28  to  14.  This  would  reduce  the  cost  per  horse-power 
from  $133  to  $66.50  in  the  first  instance,  and  from  $183  to  $91.50 
in  the  second,  both  of  which  figures  are  admissible.  Obviously 
these  questions  can  be  settled  only  by  having  a  complete  survey 
made  of  the  property,  and  a  number  of  reliable  observations  of 
the  stream  flow  obtained. 

The  question  of  carrying  part  of  the  load  during  low  water 
by  means  of  an  auxiliary  steam  plant  is  also  a  subject  for  considera- 
tion in  every  prospective  hydro- electric  development. 

Taking  the  conditions  as  given  in  the  foregoing  example,  there 


14          DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

are  28  days  in  which  a  storage  equal  to  120  cu.  ft.  per  second  is 
required  to  make  the  normal  power  due  to  300  cu.  ft.  per  second 
continuous.  At  50  feet  head  and  80  per  cent,  efficiency  this  cor- 
responds to  545  H.P.  This  may  be  obtained  by  a  steam  plant 
costing  approximately  $18,000,  if  the  plant  be  of  a  simple  charac- 
ter. The  cost  of  operating  such  a  plant  would  be  about  $8  per 
diem  for  extra  labor  and  about  $28  per  diem  for  fuel  and 
extras,  or  a  total  of  $36  per  day.  The  cost  of  supplying  this 
power  for  28  days  would  therefore  be  $1,008,  which  represents 
a  capitalization  of  $12,600  taken  at  8  per  cent.  The  equivalent 
cost  then  of  a  steam-assisted  hydraulic  plant,  referred  to  water 
power  only,  as  a  basis,  and  considering  the  first  development  be- 
fore discussed,  is  $3  5,000  +  $18,000  +  $12, 600  =  $65, 600.  Obviously 
this  is  the  plant  best  adapted  to  the  conditions  since  it  is  cheaper 
than  development  No.  3,  costs  but  little  more  than  development 
No.  2 ,  and  gives  the  full  power  of  the  plant  the  year  round,  which 
neither  of  the  others  will  do. 

The  steam  auxiliary  allows  a  much  larger  development  of 
a  given  water  power  than  is  usually  obtainable  in  any  other  way. 
If  the  stream,  before  discussed  as  an  example,  supplied  500 
cu.  ft.  per  second  at  all  times  except  about  40  days  in  the  year, 
400  cu.  ft.  except  30  days,  300  cu.  ft.  except  14  days,  and  160 
cu.  ft.  as  a  minimum,  the  power  obtainable  could  be  based  on 
500  cu.  ft.  per  second,  and  with  a  proper-sized  auxiliary  steam 

500  X  50  X  .80  per  cent 

plant,  would  be  - =2,275  H-p-  %$  against 

8.8 

1,362  H.P.  when  300  cu.  ft.  per  second  are  used.  The  steam 
plant  must  be  large  enough  to  furnish  the  power  represented  by 
the  difference  between  500  and  160  cu.  ft.  per  second  or  380 
cu.  ft.  This,  at  50  foot  head,  equals  1,738  H.P.  The  cost  of 
the  steam  plant  will  be  about  $60,000. 

It  will  be  called  on  to  furnish  power  as  follows:  1,738  H.P.  for 
14  days.     Power  due  to  200  cu.  ft.  of  water  per  second  =  (500  - 
300)  for  16  days.     This  amounts  to  910  H.P.     Power  due  to  100 
cu.  ft.  of  water  per  second  (500  —  400)  for  10  days  =  455  H.P. 


GENERAL   CONDITIONS  1 5 

The  H.P.-days'  total  are:    (1,738  X  14)  =  24,300 

910  X  16  =14,550 
455  X  I0  =     4,55° 
Total 43,400  H.P.  days. 

Taking  the  cost  of  fuel,  oil,  waste,  etc.,  at  6  cents  per  H.P.-day 
and  extra  labor  at  $8  per  day,  the  annual  cost  of  operating  the 
steam  plant  will  be: 

40  days'  labor  at  $8 $320 .00 

43,000  H  P.-days  at  6  cts 2,604.00 

.  $2,924.00 

Depreciation  on  steam  plant  at  2* 

per  cent,  on  $60,000  1,200.00 


Total  cost  of  operation $4,124.00 

which  is  interest  at  8  per  cent,  on  a  capitalization  of  about  $52,000. 

Adding  together  the  actual  cost  together  with  the  equivalent 
capitalization,  the  cost  of  the  plant  to  obtain  1,700  H.P.  additional 
is  $112,000.  This  is  $66  per  H.P.,  which  is  a  low  cost  and  would 
warrant  this  character  of  development. 

Of  course,  with  change  in  any  of  the  .ocal  conditions,  these 
figures  would  undergo  variation  which  might  be  so  considerable 
as  to  change  the  result  completely  and  make  some  other  course 
advisable.  The  foregoing  is  all  given  simply  to  indicate  the  fac- 
tors involved  in  determining  the  proper  form  of  development 
and  to  show  how  engineers  proceed  in  arriving  at  their  conclu- 
sions. The  main  object  always  to  be  kept  in  mind  is  the  produc- 
tion of  the  most  dividends  and  making  the  development  at  the 
lowest  possible  cost. 

*  Taken  at  this  figure  because  of  the  short  period  of  plant  operation  during  the 
year. 


CHAPTER    II. 
DAMS. 

BEFORE  discussing  the  various  types  of  dams  and  their  relative 
merits  it  is  necessary  to  investigate  the  forces  acting  to  rupture  or 
overturn  them. 

In  determining  the  stability  of  dams  it  is  essential  to  find  the 
centre  of  gravity  of  the  section.  Following  are  a  few  simple  rules. 

For  a  section  like  Fig.  2  or  any  quadrilateral  having  two  paral- 
lel sides,  bisect  the  parallel  sides  and  join  the  bisections  with  a 
line  Thus  bisect  A  B  at  Z  and  C  D  at  W  and  join  these  points 
by  the  line  Z  W.  Extend  each  of  the  parallel  sides,  one  in  one 


FIG.  2. 

direction,  the  other  in  the  opposite  direction,  the  amount  of  the 
extension  of  each  side  being  equal  to  the  length  of  the  opposite 
side.  Join  the  ends  of  these  extensions  by  a  line.  The  intersec- 
tion of  this  line  with  the  line  joining  the  bisected  sides  is  the  centre 
of  gravity.  Thus,  A  B  is  extended  to  the  right  an  amount  equal 
to  C  D,  while  C  D  is  extended  toward  the  left  by  an  amount  equal 

16 


DAMS 


to  A    B.    The  line  Y  X  joining  the  ends   of  these  extensions 
intersects  line  Z  W  at  G,  which  point  is  the  centre  of  gravity. 

The  centre  of  gravity  of  a  triangle  is  on  the  line  joining  the  up- 
per angle  with  the  middle  point  of  the  base  and  is  one-third  the 


FIG.  3. 

altitude  of  the  triangle  upward  from  the  base.     Fig.  3  indicates 
the  location  of  the  centre  of  gravity  of  triangular  sections. 

The  centre  of  gravity  of  a  figure  like  that  shown  in  Fig.  4  may 
be  obtained  by  dividing  it  into  two  parts  such  as  A  B  E  K  and  find- 


FIG.  4. 

ing  its  centre  of  gravity  as  at  g  and  C  K  D  and  finding  its,  as  at 
g.    The  centre  of  gravity  of  the  figure  is  on  the  line  joining  these 
2 


i8 


DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 


two  separate  centres.  Then  re-divide  the  figure  into  two  other 
forms  such  as  A  B  F  C  and  F  C  E  D.  Take  their  respective 
centres  of  gravity  at  g"  and  g'"  and  join  them  by  a  line.  The  inter- 
section G  of  the  two  lines  joining  the  two  sets  of  cen- 
tres of  gravity  is  the  centre  of  gravity  of  the  figure. 

For  contours  like  Fig.  5,  it  is  sufficiently  accurate  to 
assume  them  to  be  as  shown  in  the  dotted  lines,  giving 
a  quadrilateral  with   two   parallel  sides 
on  a  rectangle.     The  centre  of  gravity  is 
easily  found  as  above. 

In  Fig.  6  is  indicated  in  outline  the 
section  through  a  dam  with  the  water 
backed  up  behind  it. 


FIG.  5. 


Consider  one  foot  of  length  of  the  dam.     The  pressure  of  the 
water  against  the  dam  at  the  bottom  is  equal  to  the  weight  of  one 


cubic  foot  of  water  multiplied  by  the  depth  in  feet;  i.e.,  if  h  =  the 
depth  in  feet,  the  water  pressure  at  the  bottom  of  the  dam,  per  foot 
length  of  dam,  is  62 . 5  X  h.  To  make  this  clear  refer  to  Fig.  7. 


DAMS 


Consider  a  dam  with  a  depth  of  water  behind  it  of  10  ft.  Take 
a  prism  of  water  one  foot  wide  measured  along  the  length  of  the 
dam  and  one  foot  long  measured  back  from  the  dam.  This  prism 
contains  10  cubic  feet  of  water  weighing  62.5  X  10  or  625  Ibs. 


Its  area  of  support  at  the  bottom  is  one  square  foot.  Therefore 
the  pressure  at  the  bottom  is  625  Ibs.  per  square  foot,  which  is 
the  same  as  62 . 5  X  h,  when  h  =  depth  of  water  in  feet.  The  depth 
of  water  at  the  top  being  zero,  the  pressure  at  the  top  is  likewise 
zero.  The  average  pressure  per  square  foot  of  surface  against 
the  dam,  tending  to  push  it  out  of  position,  is  the  average  of  the 
top  and  bottom  pressures,  which  is  one-half  the  sum  of  the  two. 
o  -|-  W  h  -r-  2  =  J  W  /*,  is  therefore  the  average  pressure  per  square 
foot  against  the  dam,  W  being  the  weight  of  a  cubic  foot  of  water. 
The  total  pressure  from  top  to  bottom  of  the  dam  (per  foot 
of  horizontal  length)  is  obviously  equal  to  the  average  pressure 
per  square  foot  multiplied  by  the  height  in  feet;  or  is  equal  to 

W  W 

J  W/&  X  &  =  —    — .     The  dam  must  therefore  be  amply  strong  for 


each  foot  length  to  resist  the  pressure  equal  to 


62.5 


or,  in  metric 


20          DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

measurements,  the  pressure  per  metre  length  of  the  dam  is  480  Hl 
kilos  when  h  =  depth  in  metres.  This  covers  only  the  effect  of  the 
tendency  of  the  water  to  push  the  dam  down  stream.  As  a  matter 
of  fact  dams  most  often  fail  by  overturning. 

The  forces  involved  here  are  not  difficult  to  understand  and 
may  be  easily  understood  by  referring  to  Fig.  6. 

The  diagonal  line  O  A  is  the  indicator  of  the  horizontal  press- 
ure against  the  face  of  the  dam  at  any  depth  of  water.  Thus, 
if  the  diagram  be  drawn  to  some  convenient  scale,  so  that  the 
depth  h  is  equal  to  the  number  of  feet  depth  of  water  and  the 
distance  B  A  is  equal  to  62 . 5  X  h  to  the  same  or  any  other  con- 
venient scale,  then  the  horizontal  distance  from  the  face  line  of 
the  dam  O  B  to  the  diagonal  O  A  at  any  vertical  point  will  be  equal 
to  the  horizontal  pressure  against  the  surface  of  the  dam  at  that 
depth.  Thus  plt  f2,  ft,  p4  are  the  different  pressures  at  the  various 
depths  taken.  Mathematically,  the  area  of  the  triangle  O  A  B  is 
equal  to  the  total  horizontal  pressure  of  the  water.  The  area  of 
any  triangle  is  equal  to  one  half  the  product  of  its  base  by  its  alti- 
tude. In  this  case  the  base  is  W  h  while  the  altitude  is  h,  and  half 
the  product  of  these  two  is  equal  to  J  W  h2  which  is  identical  with 
the  result  previously  arrived  at  in  another  manner. 

Assume  that  the  entire  thrust  of  the  water  is  concentrated 
at  the  centre  of  pressure  which  corresponds  to  the  centre  of  gravity 
of  the  triangle  O  A  B.  The  centre  of  gravity  of  any  triangle  is 
at  one-third  the  vertical  height  of  the  triangle  above  the  base. 
This  point  is  indicated  by  g  in  Fig.  6.  The  pressure  to  overturn  the 
dam  is  J  W  h2  and  it  has  a  lever  arm  of  £  h  through  which  it  acts. 
The  overturning  moment  therefore  is  the  product  of  the  force 
multiplied  by  its  lever  arm  =  |  W2  h  X  J  h  =  J  W  h3.  Substituting 
the  value  of  W  =  62.5  Ibs.,  the  formula  becomes  M  =  io.4  h3, 
M  being  the  overturning  moment  of  the  water  in  pounds.  In 
metric  measurements  this  is  equal  to  160  h3  kilos  per  metre  length 
of  dam  where  h  =  depth  of  water  in  metres.  To  resist  this  overturn- 
ing moment  the  weight  of  one  foot  length  of  the  dam,  multiplied 
by  its  lever  arm  of  action,  must  be  equal  to  or  greater  than  M. 


DAMS  21 

Call  w  the  weight  per  cubic  foot  of  the  material  of  which 
the  dam  is  composed.  Assume  a  contour  or  shape  of  the  section 
of  the  dam  and  compute  the  area  of  this  cross-section.  The  square 
feet  cross-section  are  numerically  equal  to  the  cubic  feet  in  one  foot 
length  of  dam.  If  the  cross- section  of  the  dam  is  F.  square  feet, 
its  weight  per  foot  length  will  then  be  equal  to  w  F  Ibs. 

Assume  that  this  weight  acts  downward  through  the  centre 
of  gravity  of  the  cross-section  of  the  dam.  It  being  still  further 
assumed  that  when  dams  overturn  they  rotate  about  the  rear 
lower  edge  or  "toe,"  the  lever  arm  through  which  the  weight  of 
the  dam  acts  is  the  horizontal  distance  from  the  rear  toe  to  the 
line  of  the  centre  of  gravity.  Call  this  distance  L.  Then  w  F  L 
is  the  moment  of  the  weight  of  the  dam  to  resist  overturning,  and 
this  should  be  from  three  to  four  times  as  great  as  the  moment  of 
the  water  pressure  acting  to  overturn  it.  This  formula  also  holds 
if  w  =  weight  per  cubic  metre,  F  =  cross-section  of  dam  in  square 
metres  and  L  =  the  lever  arm  of  the  centre  of  gravity  of  the  dam 
in  metres. 

In  Fig.  6,  A  represents  the  location  of  the  centre  of  gravity 
of  the  cross-section  of  the  dam,  and  F  is  its  area  in  square  feet, 
the  weight  per  foot  length  of  dam  being  ly  F  as  shown.  L  is  the 
horizontal  distance  from  the  toe  of  the  dam  to  the  line  through  the 
centre  of  gravity,  and  the  moment  to  resist  overturning  is  w  F  L  as 
shown. 

It  is  not  sufficient,  however,  to  consider  only  the  moment  of  the 
entire  cross-section  of  the  dam  about  the  toe. 

Fig.  8  shows  the  necessity  for  additional  computations. 

In  this  figure,  although  the  area  F  is  somewhat  smaller  than 
in  Fig.  6,  the  lever  arm  L  is  greater  and  the  product  w  F  L  is  prac- 
tically as  great.  The  dam  shown  in  Fig.  8,  however,  would  fail 
by  the  overturning  of  some  portion  of  the  upper  section. 

To  proportion  a  dam  properly  it,  therefore,  -is  necessary  to  make 
computations  for  several  sections — not  less  than  three  and  usually 
five.  This  is  done  by  dividing  the  figure  into  the  number  of  hori- 
zontal sections  desired.  Fig.  8  is  divided  into  three  sections  as 


22 


DEVELOPMENT  AND   DISTRIBUTION  OF   WATER   POWER 


shown,  the  first  being  from  the  top  down  to  the  line  CE,  the  second 
from  the  top  down  to  the  line  O  K,  and  the  third  from  top  to  bot- 
tom, including  the  entire  structure.  Considering  now  the  first 
section,  the  overturning  moment  of  the  water  is  10.4  h*.  hl 
being  the  depth  of  water  down  to  line  C  E.  Call  the  area  of  sec- 


FIG.  8. 

tion  of  the  dam  DEC  included  between  the  upper  edge  and  the 
line  C  F  equal  to  F  and  the  horizontal  distance  between  its  centre 
of  gravity  and  the  rear  face  of  the  dam  where  C  E  intersects  it 
equal  to  L17  the  weight  per  cubic  foot  of  material  being  w,  then 
the  resistance  of  the  upper  section  to  overturning  about  the  line 
C  E  is  w  FJ  Lj  and  this  must  be  three  or  four  times  as  great  as  the 
overturning  water  pressure  10.4  h*.  Similarly  the  overturning 
water  pressure  about  line  S  K  is  10.4  h23,  h2  being  the  depth  of 
water  down  to  line  S  K.  The  resistance  to  overturning  is  w  F2  L2 
in  which  F2  =  area  of  section  from  the  top  down  to  line  S  K, 


DAMS  23 

and  L2  is  the  horizontal  distance  of  the  centre  of  gravity  of  this 
section  from  the  rear  surface  of  the  dam.  In  the  same  manner 
the  total  water  pressure  and  resistance  of  whole  dam  are  com- 
puted. All  the  computations  should  show  the  dam  amply  strong 
at  ever}7  point.  If  any  section  taken  shows  too  small  a  re- 
sisting moment  the  dam  must  be  thickened  at  that  section  until 
the  calculations  show  it  to  be  safe.  There  are  mathematical  for- 
mulae for  computing  the  contour  or  form  of  the  cross-section  of  a 
dam  made  of  any  given  material,  but  the  easiest,  safest,  and 
simplest  way  to  lay  out  the  cross- section  is,  by  first  assuming  a  shape 


FIG.  9. 

and  then  computing  the  relative  overturning  effects  of  the  water, 
and  the  resistance  of  each  of  several  sections  of  the  dam  as  before 
indicated.  By  altering  the  different  sections  to  correspond  to  the 
computed  requirements,  making  thicker  in  some  places  and  thinner 
in  others,  a  proper  form  of  cross-section  can  be  obtained. 

One  of  the  general  rules  in  designing  dams  is  to  take  the  re- 
sultant of  the  overturning  force  and  the  opposing  stress,  and  note 
where  this  resultant  intersects  the  bottom  line  of  the  dam.  If 
the  intersection  falls  within  the  middle  third — i.e.,  the  middle  one 


24          DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

of  three  equal  lengths  into  which  the  bottom  line  of  the  dam  con- 
tour is  divided — the  dam  is  considered  safe.  Thus  in  Fig.  9,  G 
is  the  centre  of  gravity  of  the  cross-section  of  the  dam,  and  the  down- 
ward vertical  line  G  M  passing  through  the  centre  of  gravity  rep- 
resents to  some  scale  the  value  of  w  F  or  the  weight  of  the  dam 
per  foot  length,  while  G  N,  also  passing  through  the  centre  of  gravity 


FIG.  10. 

and  at  right  angles  to  G  M,  represents  to  the  same  scale  the  value 
of  the  water  pressure  per  foot  length  of  dam  =  10.4  h3.  Com- 
pleting the  parallelogram  on  G  M  and  G  N  their  resultant  is  G  R, 
intersecting  the  base  line  at  O  which  is  well  within  the  middle 
third. 

This  method  of  determining  the  stability  of  a  dam  is  applied 
also  to  separate  sections  as  previously  described. 

When  dams  are  constructed  with  the  up-stream  face  sloping, 
the  stability  is  greatly  increased,  as  the  weight  of  the  water  tends 
to  hold  the  dam  against  overturning.  Thus  in  Fig.  10,  if  K  L  M  N 


DAMS  25 

be  the  contour  of  the  dam,  the  centre  of  gravity,  found  by  the  con- 
struction before  described,  is  at  G. 

The  downward  force  acting  at  G  due  to  the  weight  of  the  dam 
is  G  Y.  A  B  is  the  horizontal  pressure  =  10.4  h3  acting  hori- 
zontally at  a  distance  of  %  h  above  the  bottom  of  the. dam,  while 
g  A  is  the  vertical  pressure  of  the  water  =  J  W  J  //  or  3 1.25 X  JXh 
acting  downward  through  the  centre  of  gravity  of  the  triangle 
L  F  K  which  represents  the  mass  of  water  supported  by  the 
dam  W  being  the  weight  per  cubic  foot  of  the  water.  The  re- 
sultant of  these  two  forces  is  found  by  completing  the  parallelo- 
gram A  B  c  g.  It  is  equal,  algebraically,  to 


\X(io.4  /*3)2  +   (31.25  h  J)2 

but  it  is  easier  to  find  this  value  graphically,  which  from  the 
figure  is  equal  to  g  B  and  has  a  direction  perpendicular  to  K  L. 

To  find  the  effect  of  this  resultant  force  on  the  stability  of  the 
dam,  combine  it  with  the  force  due  to  the  weight  of  the  dam 
acting  through  the  centre  of  gravity  G,  and  equal  to  G  Y. 
From  point  O  where  G  B  extended  intersects  G  F,  extend  G  F  to 
5,  O  S  being  equal  to  G  F.  Draw  5  V  equal  to  g  B  and  com- 
plete the  parallelogram.  The  resultant  is  O  V,  which  cuts  the  foot 
of  the  dam  nearly  underneath  the  centre  of  gravity  and  thus  shows 
a  large  factor  of  safety. 

In  designing  dams  special  care  must  be  given  to  three  important 
factors  which  are : — 

(1)  The  spillway — i.e.,  that  portion  of  the  dam  over  which 
the  excess  water  pours — must  be  sufficiently  long  to  pass  over  it  all 
the  water  in  time  of  heaviest  flood,  without  the  water  rising  too 
high  in  flowing  over  it.     For  this  reason  it  is  not  always  best  to  lo- 
cate a  dam  in  the  narrowest  part  of  a  stream,  as  the  spillway  might 
be  too  short  if  the  stream  were  subject  to  heavy  floods.     Whether 
a  dam  can  be  made  very  short  or  not  depends  largely  on  the  varia- 
tion in  flow  during  the  year  and  particularly  on  the  maximum  flow. 

(2)  The  dam  in  every    case,  no  matter  how  constructed  or 
of  what   material,  must  rest  on  a  solid  foundation.     All  earth, 


26 


DEVELOPMENT   AND   DISTRIBUTION  OF   WATER   POWER 


sand,  loose  rock,  and  other  removable  materials  on  the  river  bot- 
tom should  be  removed  and  the  river  bottom  excavated  until  rock 
or  hard-pan  is  reached.  Too  much  care  cannot  be  exercised 
in  this  matter.  Usually  after  reaching  rock  bottom  a  shallow 
channel  should  be  blasted  out  in  which  the  bottom  of  the  dam 
may  rest.  Failure  to  provide  proper  foundation  will  result  in  fail- 
ure of  the  dam,  no  matter  how  well  it  may  be  built  otherwise. 

(3)  Proper  provision  must  be  made  for  preventing  the  falling 
water,  which  pours  over  the  spillway,  from  washing  out  the  founda- 
tion or  eroding  the  dam  itself.  Usually  the  dam  is  constructed 


K-0.1-/1— * 


to  carry  the  water  down  gently  either  on  an  incline  or  a  curved 
surface,  or  in  some  kinds  of  timber  dams  the  rear  face  is  a  series 
of  short  steps,  so  that  the  water  falls  easily  from  one  level  to  the 
next. 

There  are  several  types  of  dams,  and  the  construction  adopted 
depends  on  the  size,  height,  materials  available,  character  of  the 
stream  bed,  and  the  fluctuation  in  the  stream  flow.  All  these  con- 
siderations are  modified  by  the  funds  available  and  other  com- 
mercial factors. 

The  dams  in  general  use  are:  earthen,  timber,  masonry,  and 
reinforced  concrete. 

Earthen  dams  are  un  suited  for  any  situations  except  for  very 
low,  short,  deflecting  dams  where  they  serve  merely  to  turn  the 


DAMS  27 

water  into  a  canal  or  pipe.  In  no  case  can  they  be  successfully 
used  where  the  water  ever  passes  over  the  crest.  Their  height 
should  never  exceed  forty  feet  unless  they  are  reinforced  by  an  in- 
ternal core  wall  of  brick  or  masonry.  If  thus  strengthened  the 
height  may  be  carried  up  to  sixty  feet. 

Fig.  ii  shows  the  general  dimensions  of  an  earthen  dam  hav- 
ing a  masonry  core. 

If  h  =  height  of  the  dam,  the  thickness  through  at  the  toe  or 
bottom  should  be  2.5  to  3.5  h,  and  the  top  thickness  should  be 
not  less  than  0.4  h.  Thus  for  a  dam  12  feet  high,  h=  12.  Thick- 
ness through  at  the  bottom  =  25  X  12=30  feet.  Thickness  at 
top  =  0.4  X  12  =  4.8  feet  =  4  feet  10  inches.  The  thickness  of 
masonry  core  walls  should  be  approximately  as  follows: 

For  dams  up  to  15  feet  high 18  inches 

"       "    from  15  feet  to  25  feet  high 24      " 

"       "        "     25     "     "40     "       "       30      " 

The  best  material  for  earthen  dams  is  a  mixture  of  gravel  and 
clay.  Almost  any  proportions  of  mixture  will  make  a  good  dam, 
though  one-fourth  clay  to  three-fourths  gravel  is  a  common  propor- 
tion. Colonel  Fanning  recommends  as  a  standard  mixture  the 
following,  all  proportions  being  by  measurement: 

100  parts  coarse  gravel 
33    "       fine  gravel 
15     "      sand 
20    "      clay 

Timber  dams  can  be  used  in  nearly  any  situation.  They  have 
the  merit  of  being  cheap,  easy  to  build,  and  quickly  put  in  place. 
They  have  the  disadvantage,  however,  of  requiring  frequent  re- 
pairs above  the  water-line.  Of  course  those  portions  that  are  com- 
pletely submerged  will  last  indefinitely.  They  cost  from  one-third 
to  five-eighths  as  much  as  a  good  masonry  dam,  depending  on  the 
locality.  In  many  cases  they  serve  the  purpose  admirably  and 
enable  a  development  to  be  made  and  put  in  commission  where  the 
expenditure  would  be  prohibitive  if  a  masonry  dam  were  erected. 
Their  forms  are  numerous,  and  could  not  all  be  here  given  in 


28 


DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 


proper  detail,  but  nearly  any  engineer  or  constructor  can  design  a 
wooden  dam  to  resist  the  forces  it  may  be  subjected  to. 

Examples  of  timber  dams  are  shown  in  Figs.  12  and  13.     Fig. 
12  shows  a  crib  dam,  made  by  piling  up  logs  in  square  "cribs" 


6offefv         - 
vFllled  to+lQf 

I   PudSieCUy 
i  <&d  Gravel 

^  I 


FIG.  12. 

and  filling  these  in  with  loose  stone.  The  upper  surface  is  covered 
with  planking  two  inches  thick,  and  the  rear  of  the  dam  forms  a 
succession  of  steps  whereby  the  overflow  water  falls  gently  to  the 
lower  level  of  the  tail  race. 

Fig.  13  shows  another  form  of  wooden  dam,  called  a  frame  dam. 
The  dimensions  are  given  and  the  construction  is  obvious  from  the 


FIG.  13. 

figure.    The  framework  is  filled  with  loose  stone  or  gravel  and 
covered  over  with  planking. 

In  many  instances  where  the  maximum  floods  are  small  and 


DAMS 


29 


tlie  river  is  wide,  earthen  dams  are  built  nearly  all  the  way  across 
the  stream  and  timber  spillways  fill  the  rest  of  the  space,  and  thus 
a  combination  earth-and-timber  dam  is  formed.  The  earth  por- 
tion must  be  enough  higher  than  the  timber  part  to  prevent  water 
from  ever  passing  over  the  former,  all  water  flowing  over  the  tim- 
ber part  only.  The  excess  height  of  the  earth  dam  above  the  tim- 


FIG.  14. 

ber  spillway  depends,  of  course,  on  the  length  of  the  spillway  and 
the  maximum  flow  in  time  of  flood. 

Masonry  Dams. — These  are  the  most  generally  used,  and,  though 
the  most  expensive,  are  the  most  reliable  and  satisfactory,  requir- 
ing a  minimum  amount  for  repairs  and  maintenance. 

Fig.  6  shows  the  usual  form  of  cross- section  of  a  masonry  dam. 
As  will  be  seen,  the  rear  face  of  the  dam  is  curved  in  such  a  manner 
that  the  overflowing  water  follows  smoothly  down  against  the  rear 
face,  changing  its  direction  continually  and  finally  reaching  the  tail 
water  without  impact.  The  two  curves  which  are  reversed  to  each 
other,  and  which  outline  the  shape  of  the  rear  wall,  are  parabolas. 

Masonry  dams  have  their  approximate  contours  computed  as 
before  outlined  in  this  chapter,  and  the  smooth  curves  are  drawn 
to  adhere  as  closely  as  possible  to  the  computed  outline. 

The  materials  used  in  dams  of  this  type  are  widely  variable. 
Some  are  made  of  cut  stone,  laid  up  in  hydraulic-cement  mortar. 


30         DEVELOPMENT  AND   DISTRIBUTION  OF   WATER  POWER 

A  usual  construction  is  to  lay  up  the  front  and  rear  walls  of  cut 
stone,  and  fill  in  between  these  with  concrete. 

Cyclopean  masonry  is  also  used  in  some  instances.  This  is 
made  up  of  rough  stones  of  various  sizes  and  shapes,  ranging 
from  the  size  of  a  barrel  down  to  the  size  of  a  man's  fist.  The 
smaller  stones  fill  the  interstices  between  the  greater  stones,  all 
being  laid  in  Portland- cement  mortar. 

Some  dams  are  now  made  altogether  of  concrete,  which  is 
firmly  rammed,  as  the  construction  proceeds,  to  solidify  the  mass. 


FIG.  15. 

More  recently  the  growing  use  of  steel-reinforced  concrete  has  ex- 
tended to  hydraulic  work,  and  the  dams  are  strengthened  by  the  use 
of  reinforcing  steel  forms.  These  concrete  dams  are  of  the  so-called 
"gravity"  type.  That  is,  they  have  a  sloping  face  on  the  up- 
stream side,  and  use  the  downward  thrust  of  the  water  to  give 
stability  to  the  structure.  In  this  way  the  weight  of  the  dam  may 
be  greatly  diminished  and  the  cost  proportionally  decreased. 
Fig.  1 4^ shows  a  section  through  a  dam  of  this  character.  As  may 


DAMS  31 

be  seen,  it  is  hollow  and  depends  for  its  effectiveness  on  the  weight 
of  the  water  rather  than  the  absolute  weight  of  the  dam  itself. 

Fig.  15  is  a  masonry  dam  in  the  course  of  construction,  its 
general  form  being  that  indicated  in  Fig.  6.  Fig.  16  is  a  picture  of 
this  dam  completed,  with  water  pouring  over  the  spillway.  The  effect 
of  the  curved  rear  face  in  carrying  the  water  smoothly  down  is  seen. 

Dams  must  always  be  constructed  with  drain  gates  near  the 


FIG.  1 6. 

bottom,  so  that,  in  case  of  repairs  being  necessary,  the  water  may 
be  drawn  down  and  the  entire  reservoir  drained.  Usually  these 
gates  slide  upward  to  open,  being  moved  by  a  rack  and  pinion 
or,  in  some  instances,  a  screw. 

A  drain  gate  should  also  be  provided  near  the  top  of  the  dam, 
to  allow  accumulated  trash  and  floating  debris  to  pass  through 
whenever  this  upper  gate  is  opened.  This  gate  also  helps  to  dis- 
charge water  in  time  of  heavy  flood. 


CHAPTER  III. 
CANALS  AND  FLUMES. 

WHEN  the  location  of  a  dam  is  decided  on,  if  it  be  at  the  foot 
of  the  fall  or  shoals,  the  power-house  too  will  be  located  there,  and 
no  conducting  of  water  will  be  necessary.  If,  however,  the  dam 
is  placed  some  distance  above  the  foot  of  the  shoals,  the  water 
must  be  conducted  to  the  power-house,  which  is  always  at  the  foot 
of  the  fall.  The  oldest  method  of  carrying  the  water  is  by  means 


FIG.  17. 

of  a  level  canal  running  along  the  hillside  until  the  power  house 
is  reached,  and  then  being  carried  down  through  a  pipe  to  the 
water  wheels.  Where  necessary  for  the  canal  to  cross  gulleys, 
ravines,  or  other  depressions,  the  crossing  is  made  by  means  of  a 
trough  or  flume  supported  on  a  trestle-work.  Fig.  17  shows  a 
wooden  flume  carrying  water  across  a  depression.  Except  under 
unusual  conditions,  however,  it  is  better  and  cheaper  to  use  pipe 
to  convey  the  water  to  the  power-house.  The  pipe  does  not  have 
to  be  laid  level,  but  can  follow  the  contour  of  the  shortest  route 
from  the  dam  to  the  power-house.  For  small  powers,  cast-iron 

32 


CANALS   AND   FLUMES 


33 


pipe  is  sometimes  used;  for  large  quantities  of  water,  wrought-iron 
pipe  is  employed,  while  for  low  head,  wood  stave  pipe  held  together 
by  iron  bands  is  used. 

In  some  cases  that  portion  of  the  pipe  near  the  dam  and  where 
the  pressure  is  low — say  up  to  forty  feet  head — is  made  of  wood  stave 
pipe,  while  the  lower  portion  of  the  conduit  is  made  of  riveted 
wrought-iron  pipe,  which  gradually  increases  in  thickness  as  the 
pipe  sinks  further  and  further  below  the  reservoir  level,  that  is,  as 


FIG.  i 8. 

the  pressure  on  the  pipe  increases,  the  strength  of  the  pipe  is  in- 
creased. 

Fig.  1 8  shows  a  wood  stave  pipe  which  forms  the  upper  or  low- 
pressure  portion  of  a  water  conduit  for  a  power  station  in  the 
Western  States. 

Riveted  wrought-iron  pipe  costs  about  double  that  of  wood 
stave  pipe.  Following  is  a  table  of  approximate  costs  per  foot  of 
riveted  pipe  of  various  diameters,  to  withstand  pressure  due  to 
250  foot  head. 

These  costs  change  with  increase  or  decrease  of  head.     The 

figures  are  based  on  a  unit  price  of  4^  cents  per  Ib.     To  compute 

the  weight  of  any  pipe  take  the  circumference  X  length.     This 

gives  the  area  in  square  feet.    Multiply  the  area  by  2.5  and  this 

3 


Inches 
24  

$2.  3  ? 

26   . 

2    60 

28   ... 

•2     OO 

T.Q  .  . 

•7      I   C 

?6 

c   OO 

4O         . 

6  4.O 

42  .  . 

7.OO 

34         DEVELOPMENT  AND   DISTRIBUTION  OF   WATER   POWER 

product  by  the  number  of  i6ths  of  an  inch  thickness  of  the  plate. 
Add  to  this  10  per  cent,  for  lap  and  rivets.  Thus  a  pipe  60  inches 
in  diameter  and  -f$  inches  thick  weighs  per  100  feet  :  100  X  3.1416 
X  fl  X  2-5  x  5  =  II>8Sl  Ibs.  Add  10  per  cent,  and  the  total 
weight  becomes  13,069  Ibs. 

TABLE  No.  2.  —  COSTS  OF  STEEL  PIPE. 

Inches 
10  ....................  $  .72 

12  ....................  82 

14  ...................  98 

16  ...................    1.20 

18  ....................    1.40 

20  ....................      2.OO 

22  ....................     2.25 

The  transmission  of  water  through  pipes  is  accompanied  by 
a  loss  of  head  and  this  loss  means  that,  for  a  given  quantity  of  water, 
less  power  is  available  at  the  water  wheels.  The  larger  the  pipe 
the  less  is  the  loss  of  head,  but  the  greater  is  the  cost  of  the  pipe. 
Therefore,  this  feature  brings  in  another  commercial  factor  as 
to  the  size  of  pipe  which  represents  the  smallest  loss  of  power  and 
interest  on  the  invested  capital.  Where  the  power  is  small  and  its 
value  high,  more  money  can  be  invested  in  pipe  than  where  the 
power  is  great  and  its  value  low.  The  average  size  of  pipe  adopted 
in  the  United  States  is  that  which  gives  a  velocity  of  water  of  from 
4  to  6  feet,  or  from  ij  to  2  metres  per  second.  Velocities  as  low 
as  two  feet  (0.6  metre)  and  as  high  as  12  feet  (3.6  metres)  per 
second  are  known,  but  the  figures  given  represent  fair  average 
practice. 

If  Q  =  quantity  of  water  in  cubic  feet  required  per  second 
for  a  given  turbine  under  a  specified  head,  the  diameter  of  the  pipe 


required  with  a  given  velocity  is  D  »  1.137  y         in  which  Q  = 

quantity  of  water  flowing  in  cubic  feet  per  second,  V  =  velocity 
of  flow  in  feet  per  second.  This  formula  also  holds  for  metric 
measurements.  If  D  =  diameter  of  pipe  in  metres,  Q  =  cubic  metres 
of  water  per  second,  and  V=  velocity  in  metres  per  second. 


CANALS   AND   FLUMES  35 

The  loss  of  head  is  computed  from  the  formula 

+  0.0234  V2), 


in  which 

h  =  \oss  of  head  in  feet; 

/  =  a  variable  factor  depending  for  its  value  on  the  character  of  the 

pipe  surface; 
/  =  length  of  pipe  in  feet  ; 
d=  diameter  of  pipe  in  feet; 
V  =  velocity  of  flow  of  water  in  feet  per  second. 

Values  of  /  are  as  follows  : 
For  smooth-planed  wood-stave  pipe  =0.005    I  i-j  ---  J; 

For  smooth-steel  plate  pipe  =  0.0065  (  i  -f-  -  -  I  ; 

V       i2d/ 

For  old  and  pitted  steel  pipe  =  o.oi   (  i-f  —     ). 

V        1  2d/ 


In  arriving  at  the  actual  head  acting  on  the  water  wheels  the 
frictional  head  loss,  computed  as  above,  must  be  deducted  from 
the  total  head  to  obtain  the  net  effective  head. 

Where  an  open  canal  is  used  to  convey  the  water  to  the  power 
station,  it  is  often  practicable  to  make  the  side  next  the  stream 
assist  the  spillway  by  constructing  it  to  allow  water  to  flow  over 
the  edge  without  injury  to  the  canal  bank.  In  such  cases  very 
short  dams  may  be  used,  the  length  of  spillway  being  made  suf- 
ficiently great  by  using  the  side  of  the  canal. 

At  the  point  where  a  canal  joins  the  dam  and  the  inflowing 
water  enters,  it  should  be  protected  against  both  heavy  and 
light  trash  which  floats  down  stream  and  accumulates.  Stop  logs 
placed  out  a  few  feet  from  the  canal  mouth  serve  to  arrest  the  en- 
trance of  heavy  timbers  or  branches  of  trees.  These  stop  logs  are 
simply  booms  made  of  heavy  wooden  timbers  laid  across  the  stream, 
which  float  on  the  water,  but  are  anchored  to  prevent  them  from 


36          DEVELOPMENT   AND    DISTRIBUTION   OF   WATER   POWER 

moving  from  their  positions.  Trash  racks  must  be  put  in  place 
to  stop  the  smaller  and  lighter  trash,  such  as  twigs,  and  particularly 
dead  leaves.  These  trash  racks  are  made  of  flat  rectangular  bars 
of  iron  or  wood — preferably  the  former — which  are  put  in  an  almost 
vertical  position  with  the  narrow  edge  to  the  inflowing  water,  each 
bar  extending  from  a  point  four  or  five  feet  below  the  surface  of 
the  water  to  about  five  feet  above  it.  The  bars  are  spaced  from 
i  to  2  inches  (2^  to  5  cent  metres)  apart  and  are  fastened  together 
to  form  sections,  each  section  being  from  2  to  3  feet  wide.  These 
sections,  which  are  in  effect  vertical  gratings,  are  held  by  a  frame- 
work which  is  generally  arranged  with  slides,  so  that  each  section 
may  be  hoisted  up  and  cleaned  when  necessary,  and  afterward 
slipped  back  into  place. 

Forebays  should  also  be  provided.  These  are  sirrply  quiet 
ponds  which  are  made  by  running  low  walls  out  into  the  water 
from  the  mouth  of  the  canal,  the  walls  spreading  further  and  fur- 
ther apart  as  they  extend  outward.  It  is  also  customary  to  pro- 
vide a  forebay  at  the  lower  end  of  the  canal,  made  by  widening 
out  the  canal  to  three  or  four  times  its  normal  width,  just  at  the 
power-house.  The  length  of  the  forebay  is  about  the  saire  as  its 
width.  Its  object  is  to  allow  the  water  to  enter  the  water  wheels 
smoothly  and  easily  without  eddy  swirls;  and  it  is  simply  a  basin 
of  sufficient  volume  to  allow  the  incoming  water,  moving  at  some 
velocity,  to  settle  quietly  before  going  to  the  water  wheels. 

A  second  trash  rack  should  be  placed  at  the  power  station 
between  the  forebay  and  the  entrance  for  the  water  to  the  turbines. 

When  closed  pipes  are  used,  a  forebay,  trash  racks,  and  stop- 
logs  must  be  provided  at  the  mouth  of  the  pipe,  but  none,  of  course, 
at  the  power  station.  In  addition,  provision  must  be  made  to 
prevent  injury  and  possibly  rupture  of  the  pipes  from  water  ham- 
mer, which  occurs  when  the  turbine  gates  tend  to  close  too  quickly 
unless  some  preventive  measure  is  taken. 

There  are  two  methods  of  preventing  water  hammer.  One  is 
by  means  of  relief  valves,  which  are  simply  spring  pressure  valves 
very  similar  to  an  ordinary  pop  safety  valve  for  steam  boilers. 


CANALS   AND   FLUMES  37 

These  open  when  the  pressure  in  the  pipe  increases.  They  must 
be  of  ample  area.  Generally  several  are  used,  located  at  the  lower 
end  of  the  pipe,  and  their  combined  areas  should  be  equal  to  at 
least  thirty  per  cent,  of  the  area  of  the  pipe. 

The  other  method  is  the  use  of  a  standpipe.  This  is  a  verti- 
cal pipe  connected  with  the  main  pipe  at  a  point  near  the  lower 
end  of  the  latter.  This  standpipe  is  open  at  the  top  and  therefore 
must  be  high  enough  to  be  on  a  level  with  the  surface  of  the  head 
water  or  slightly  above  it.  If  the  pressure  in  the  pipe  is  normal, 
the  standpipe  simply  remains  filled  to  the  top.  A  sudden  increase 
in  pressure  in  the  main  pipe  line,  due  to  sudden  closing  of  the  tur- 
bine gate,  will  cause  water  to  flow  up  through  the  standpipe  and 
pour  over  the  top,  the  main  pipe  pressure  having  risen  above  that, 
due  to  the  head  of  water  in  the  standpipe.  The  area  of  the  stand- 
pipe  should  be  not  less  than  thirty  per  cent,  of  the  area  of  the  main 
pipe,  and  fifty  per  cent,  is  better. 

Obviously,  since  a  standpipe  must  be  as  high  as  the  head  of 
water  available  at  the  power  station,  it  is  suited  only  to  use  on  low 
heads,  say  not  above  60  feet.  It  must  be  well  braced  against 
swaying,  securely  fastened  in  place,  and  provision  must  be  made 
to  catch  and  carry  away  its  overflow.  The  water  from  it  falls 
through  a  considerable  height  and  will  quickly  erode  foundations, 
concrete  work,  and  the  like  if  allowed  to  fall  against  any  such  struc- 
tures. 

For  the  benefit  of  those  who  are  interested  in  following  further 
the  question  of  pressures  set  up  in  pipes  with  rapid  closing  and 
opening  of  water  gates,  an  abstract  of  a  paper  on  this  subject, 
presented  before  the  American  Institute  of  Electrical  Engineers 
by  the  author,  is  inserted  as  an  appendix  to  this  text. 


CHAPTER  IV. 
THE  DESIGN  OF  HYDRO -ELECTRIC  POWER-HOUSES. 

THERE  are  three  general  classes  of  power-houses.  The  first 
is  that  which  is  located  at  some  distance  away  from  the  dam  and 
the  water  conducted  to  the  power-house,  the  flow  of  water  being 
from  the  front  to  the  back  of  the  house,  passing  transversely 
under  it. 

The  second  is  that  in  which  water  is  conducted  to  the  power- 
house, passing  through  water  wheels  located  outside  the  house, 


FIG.  19. 

the  flow  of  water  being  alongside  and  parallel  to  one  of  the  outer 
walls. 

The  third  is  that  in  which  the  power-house  is  located  at  the 
dam,  the  water  passing  through  the  water  wheels  and  transversely 
under  the  house. 

In  the  first  and  third  types,  the  houses  are  built  on  a  series 

38 


U  I*  I  V  (_.  rv  -7  I    I     1 

OF 


DESIGN   OF   HYDRO-ELECTRIC    POWER-HOUSES 


39 


of  arches  of  masonry  or  concrete  running  transversely  under  the 
floor  and  which  are  sprung  from  piers  that,  in  turn,  rest  on  the 
foundations  below.  Usually  the  piers  extend  transversely  the 
whole  width  of  the  house. 

The  floor  of  the  house  is  constructed  on  the  arches,  by  filling 
in  over  them  with  masonry  or  concrete  until  a  level  surface  is 
obtained. 

In  cold  climates  where  there  is  liability  of  freezing,  the  wheels 
arc  placed  inside  the  power-house,  but  in  warmer  latitudes  they 


FIG.  20. 

are  put  outside,  with  the  stuffing-box  end  only  of  the  casing  passing 
through  the  wall  and  flush  with  the  inner  face. 

The  turbines  are  supported  on  masonry  or  structural  steel 
supports,  or,  when  located  outside  the  house,  they  sometimes  rest 
on  extensions  of  the  arches  which  project  beyond  the  wall  of  the 
house.  The  water  passes  through  the  wheels  and  is  discharged 
through  draft  tubes  to  the  tail  water  below  which  flows  through 
the  arches  underneath  the  house,  to  the  stream  bed.  When  the 
turbines  are  placed  inside  the  house  they  rest  on  the  floor  above 
the  arches. 


40          DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

The  customary  design  provides  for  an  arch  for  each  main  tur- 
bine and  one  for  two  small  exciter  turbines.  Figs.  19  and  20  show, 
generally,  power-houses  of  these  types. 

Taking  up  the  first-class  and  considering  it  more  in  detail  it 
may  be  subdivided  into  two  types,  (a)  one  in  which  the  turbines 
are  direct-connected  to  the  generators,  and  (b)  that  in  which  the 
turbines  are  belted  or  rope- connected  to  the  generators.  In  the 
former  case  the  turbines  are  set  at  such  a  level  that  their  shaft 
centres  coincide  with  the  generator-shaft  centres,  and  a  flanged 
coupling  connects  the  two  shafts.  The  generators  are  usually 


FIG.  21. 

made  with  bases  of  such  height  that  the  distance  from  the  masonry 
supporting  floor  to  the  centre  of  the  generator  shaft  is  the  same 
as  the  height  of  centre  of  the  turbine,  so  that  the  two  rest  on  the 
same  level. 

When  the  turbines  are  set  inside  the  house,  the  conducting 
tubes  pass  through  the  wall  or  under  the  archways  and  upward 
through  the  floor  to  the  wheels.  If  the  turbines  are  set  outside 
the  house,  the  stuffing-box  end  of  the  casing,  through  which  the 
drive  shaft  passes,  is  set  into  the  wall,  the  end  of  the  casing  being 
flush  with  the  inner  surface  of  the  wall  or  possibly  projecting  a 


DESIGN   OF   HYDRO-ELECTRIC   POWER-HOUSES  41 

few  inches  into  the  room.     These  remarks  apply,  of  course,  only 
to  iron-shell-encased  turbines. 


When  the  wheels  are  set  in  open  penstocks  of  masonry  or  con- 
crete, one  wall  of  the  power-house  usually  serves  as  a  wall  of  the 


42          DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

penstock.  Stuffing  boxes  fastened  into  the  wall  allow  the  turbine 
drive  shafts  to  pass  through  into  the  power-house  without  leakage 
cf  water.  Fig.  21  shows  a  cross-section  through  a  station  using 
an  iron-encased  turbine  inside  the  house  direct  connected  to  the 
generator  it  drives.  Fig.  22  shows  a  direct-connected  plant  in 
which  the  turbines  are  located  outside  the  house  in  an  open  pen- 
stock. The  supporting  arches  which  carry  the  power-house 
floor  are  clearly  indicated  in  these  sections.  As  may  be  seen  in 


FIG.  23. 

Fig.  21  the  conducting  pipe  from  the  dam  goes  directly  to  and  con- 
nects with  the  iron  casing  of  the  turbine. 

The  use  of  the  open  penstock  is  confined  to  low  heads — say  up  to 
thirty-five  feet — and  generally,  the  water  conduit  is  a  canal  or  open 
flume  which  discharges  into  the  penstock,  though  in  some  instances 
pipes  conduct  the  water  to  the  penstock.  Whenever  it  is  feasible, 
the  open  penstock  should  be  used,  as  the  regulation  obtainable 
on  the  water-wheels  is  improved  and  they  are  more  accessible  for 
inspection  and  repair. 

Some  plants  have  the  water  supplied  by  a  canal  which  ends 
in  a  forebay  near  the  power-house,  and  a  short  tube  conducts  the 
water  to  iron-encased  wheels.  Power-houses  for  such  equipments 
are  similar  to  the  arrangement  shown  in  Fig.  21. 

Power-houses  of  the  second  class,  i.e.,  where  the  discharge  water 


DESIGN  OF   HYDRO-ELECTRIC   POWER-HOUSES 


43 


from  the  turbines  does  not  pass  under  the  house,  but  alongside  of 
it,  are  usually  for  small-capacity  plants.  The  house  may  be 
supported  in  any  manner  which  seems  most  suitable  for  the  par- 
ticular situation,  no  provision  being  made  for  the  passage  of  water 
underneath  it.  Fig.  23  is  a  view  of  a  plant  of  this  type.  The  tur- 
bines are  supported  on  a  masonry  foundation  extended  upward 


FIG.  24. 

until  its  surface  is  approximately  level  with  the  power-house  floor. 
An  archway  in  the  water-wheel  foundation  provides  for  the  dis- 
charge of  water. 

Fig.  24  is  a  cross-section  of  this  plant,  showing  the  building  walls 
and  the  supporting  piers  for  the  generators,  running  down  to  bed- 
rock. 

For  small  plants  in  warm  or  temperate  climates  this  is  an  ex- 
cellent and  low-priced  form  of  construction. 


44          DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

The  most  general  construction  at  present  in  favor  is  to  build 
the  power  station  at  the  dam,  when  possible,  and  to  let  one  wall 
of  the  power-house  be  close  to  the  dam,  and  in  some  cases  the  rear 
of  the  dam  forms  one  wall  of  the  house.  This  portion  of  the  dam 
is  not  made  in  the  same  form  as  the  rest,  but  rises  much  higher  than 
the  crest  of  the  spillway  portion  and  is  simply  shaped  to  give  the 
requisite  resisting  strength,  not  curved  to  carry  away  overflow,  since 
there  is  no  passage  of  water  over  this  portion  of  the  dam;  in  fact, 
the  added  height  is  for  the  purpose  of  preventing  any  overflow 
at  that  end.  This  raised  portion  is  called  the  bulkhead. 

The  turbines  used  in  such  cases  are  almost  invariably  iron- 
encased,  their  shells  being  extended  to  pass  through  the  bulkhead 
and  receive  the  water  direct  without  the  necessity  of  using  conduct- 
ing pipes  of  any  kind. 

When  the  bulkhead  serves  as  the  power-house  wall,  the  tur- 

,bines  are  placed  inside  the  house,  their  casing  extensions  passing 

through  the  bulkhead  and  being  sealed  into  the  masonry.     The 

turbine  end  of  the  casing  being  inside  the  power-house,  the  wheels 

themselves  are  accessible  for  repairs. 

In  some  of  the  later  plants  the  power-house  wall  is  separated 
from  the  bulkhead,  there  being  a  short  space  between  the  two. 
The  turbine  casing  passes  through  bulkhead  and  across  the  in- 
tervening space  and  through  the  wall  of  the  house,  ending  just 
inside  the  wall  or  flush  with  it  at  one  end,  and  at  the  inner  bulk- 
head face  on  the  other.  Large  openings  are  made  in  the  casing, 
between  the  bulkhead  and  house  wall,  and  through  these  openings 
the  wheels  may  be  inspected  and  repaired.  They  are  closed  up 
with  steel  plates  bolted  in  place. 

The  draft  tubes  pass  down  through  the  supporting  arches — 
which  are  extended  up  to  the  bulkhead  and  joined  to  it — and  the 
water  is  discharged  below  the  floor  passing  under  it,  just  as  has 
been  before  described. 

Fig.  25  illustrates  this  method  of  construction.  The  level  of 
the  water  shows  the  height  of  the  spillway  portion  of  the  dam,  and, 
as  may  be  seen,  the  bulkhead  portion  is  much  higher  than  the  crest 


DESIGN   OF   HYDRO-ELECTRIC   POWER-HOUSES 


45 


46          DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

of  the  dam.  The  turbine  units,  in  this  case,  comprise  two  pairs  of 
double  wheels  coupled  tandem. 

In  many  instances,  the  low  speed  of  the  turbines  due  to  low 
heads  precludes  the  possibility  of  using  low-priced  dynamos  if 
direct  connected  to  the  turbines,  owing  to  their  similarly  low  speeds. 
It  therefore  becomes  necessary  to  drive  the  dynamos  by  belting 
or  rope  drives  from  the  turbines,  in  order  to  give  a  higher  speed  to 
the  generators  than  that  of  the  turbines.  In  such  plants  it  is 
customary  to  make  the  station  floor  considerably  higher  than  the 
level  on  which  the  turbines  rest,  generally  from  ten  to  twenty  feet 
higher,  and  have  the  belts  or  ropes  pass  diagonally  upward  from  the 
turbine  drive  pulley  to  that  of  the  dynamo.  The  turbines  may  be 
placed  outside  or  inside  the  house  and  may  be  in  open  penstocks 
or  steel-encased.  Usually  in  such  cases,  however,  the  water-wheels 
are  installed  in  open  penstocks  outside  the  house,  and  their  drive 
shafts  extend  through  stuffing  boxes  into  the  house  walls.  On 
the  inner  ends  of  the  shafts  are  placed  the  drive  wheels  which 
transmit  the  power  to  the  dynamos. 

When  the  hydraulic  heads  are  very  high,  impulse  wheels  of 
the  Pelton  pattern  are  used,  and  these  rotate  at  very  high  speeds. 
The  impact  of  the  water  jet  coming  from  the  supply  nozzles  is  so 
great  that  provision  must  be  made  to  prevent  the  erosion  of  power- 
house foundations  and  consequent  collapse  of  the  structure.  This 
is  done  by  providing  a  deep,  long  pool  of  water  against  the  sur- 
face of  which  the  deflected  portion  of  the  jet  strikes.  At  the  far 
end  of  the  pool  is  a  baffle  which  maintains  the  required  depth  of 
water  in  the  pool,  usually  from  five  to  eight  feet.  The  impact  of 
the  water  from  the  nozzle  being  at  an  acute  angle  to  the  pool  water 
surface,  the  jet  passes  a  considerable  distance,  diagonally,  before 
striking  the  bottom  of  the  pool,  and  its  velocity  has  practically 
been  reduced  to  zero  by  the  time  the  bottom  is  reached,  so  that  there 
is  no  scouring  or  erosive  action. 

Fig.  26  shows  a  section  through  a  power-house  of  this  character. 
The  arrangement  of  impulse  wheel  and  nozzle  is  clearly  indicated. 

In  designing  power-houses  care  must  be  taken  to  locate  the 


DESIGN   OF   HYDRO-ELECTRIC   POWER-HOUSES 


47 


water-wheels  at  a  proper  height  above  the  tail-water  level.  Where 
streams  are  reasonably  constant  in  their  volume  of  flow  and  the 
tail- water  level  does  not  vary  greatly,  the  turbines  should  be  placed 
at  a  height  of  from  8  to  12  feet — or  2\  to  3^  metres — above  the  nor- 
mal level  of  the  tail  water,  the  distance  being  measured  from  the 
centre  line  of  the  turbine.  In  cases,  however,  where  the  flow  of 
the  stream  fluctuates  greatly,  the  tail-water  level  will  also  vary 
within  wide  limits  and  the  turbines  must  be  placed  higher.  The 


FIG.  26. 

conditions  in  this  respect,  have,  in  some  instances,  required  the  tur- 
bines to  be  located  twenty  feet  above  the  normal  tail- water  level. 
The  efficiency  of  the  draft  tube  begins  to  decrease  if  its  length 
exceeds  fifteen  feet,  and  in  no  case  should  turbines  be  placed  more 
than  this  height  above  normal  tail-water  level  unless  the  conditions 
absolutely  require  a  greater  height. 

Power-houses  are  built  of  a  variety  of  materials.  The  con- 
struction most  in  favor  in  the  United  States  is  the  masonry  or  con- 
crete for  arches,  piers,  and  foundations,  brick  for  the  structure  it- 


48          DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

self,  reinforced  concrete  for  floors,  and  a  trussed  roof  of  structural 
steel,  covered  with  slate,  tiles,  or  gravel  roofing.  Iron  or  steel 
roofing  is  not  suitable  for  power-houses  because  it  " sweats"  or 
accumulates  condensed  atmospheric  moisture  on  the  under  surface. 
Whatever  be  the  method  of  construction,  the  station  should  be 
made  entirely  of  fire-proof  material. 

The  floor  space  of  the  station  should  be  sufficiently  large  to 
admit  of  getting  at  every  side  and  part  of  each  machine,  with  plenty 
of  space  between  machines  and  walls  or  between  neighboring 
machines  to  easily  pass  round  them  and  to  remove  any  part  with 
ease  and  facility. 

The  height  of  stations  varies  greatly.  The-  minimum  height 
from  floor  to  roof  trusses  should  not  be  less  than  18  feet,  but  in 
very  small  plants  this  has  been  made  as  low  as  16  feet.  For  mode- 
rate-size stations,  20  to  22  feet  is  a  fair  height,  while  26  to  28  feet 
is  usual  in  large  stations  where  the  dimensions  of  the  generators 
are  considerable. 

The  foundations  should,  when  possible,  rest  on  bed-rock. 
When  this  is  impracticable  or  if  hard-pan  cannot  be  reached,  it  is 
necessary  to  drive  piles,  cut  them  off  below  the  low-water  level 
so  that  no  portion  of  them  may  ever  become  dry,  and  put  in  a 
concrete  footing  on  top  of  the  piles.  The  number,  length,  and  size 
of  the  piles  depend  on  the  character  of  the  soil  and  the  load  to  be 
carried.  The  usual  spacing  of  piles  is  three  feet  between  centres, 
though  this  is  frequently  varied  to  suit  conditions.  No  general 
instructions  can  be  given  for  this  part  of  the  work,  as  each  case 
must  be  treated  to  cover  the  individual  conditions  that  exist. 

Nearly  every  station  is  designed  to  carry  overhead  travelling 
cranes,  by  means  of  which  the  machinery  may  be  erected  and  any 
part  easily  and  quickly  lifted  out  of  place  for  inspection  and  re- 
pairs. This  is  a  desirable  arrangement  for  large  stations  having 
many  units,  but,  in  the  opinion  of  the  author,  it  has  been  carried 
too  far  in  the  design  of  small  stations.  A  good  travelling  crane 
with  its  runway  and  supporting  structure  is  expensive,  and  in  many 
cases  the  money  spent  therefor  could  be  used  to  better  advantage 


DESIGN   OF   HYDRO-ELECTRIC    POWER-HOUSES  49 

in  providing  higher  grade  generating  equipment,  or  letting  it  re- 
main unspent.  A  heavy  set  of  short,  strong  shear  legs,  arranged 
in  tripod  form,  with  a  differential  chain  hoist,  is  all  that  is  required 
in  small  power-houses. 

The  switchboard  should  be  located  on  a  gallery  elevated  above 
the  floor  level.  The  heights  that  are  usual  are  from  seven  to  ten 
feet.  Underneath  the  rear  of  the  gallery  are  placed  brick  chambers 
in  which  are  located  the  high-tension  switches,  operated  directly 
from  the  switchboard  above. 

When  transformers  are  used,  they  arc  generally  located  in 
the  power  station  itself,  though  in  some  recent  plants  a  separate 
building  is  provided  for  their  reception.  Each  transformer  should 
be  placed  in  a  separate  brick  or  concrete  chamber,  well  ventilated 
and  provided  with  a  fire-proof  steel  door  at  the  front.  The  floor 
level  of  the  transformer  chambers  should  be  the  same  as  that  of 
the  station  floor  so  that  any  transformer  may  be  rolled  out  on  the 
rollers  placed  under  each  one  onto  the  station  floor  for  inspection 
or  repair. 

One  of  the  important  factors  in  hydraulic-power  plant  design 
is  the  proper  provision  for  removal  of  sand,  leaves,  ice,  and  trash 
from  the  water  flowing  into  the  wheels.  Sand  is  detrimental  owing 
to  its  cutting  action  on  the  water-wheel  blades;  and  in  high-head 
plants,  where  impulse  wheels  are  used  and  the  velocity  of  the  water 
is  high,  a  very  slight  amount  of  sand  will  quickly  cut  through  the 
wheel  bucket.  The  usual  way  of  removing  sand  is  to  provide 
a  settling  basin  at  the  upper  end  of  the  pipe,  where  the  water  comes 
to  rest  and  stands  long  enough  to  let  the  sand  settle  to  the  bottom 
of  the  basin. 

Surface  or  floating  ice  gives  but  little  difficulty  if  the  conducting 
pipe  is  set  into  a  forebay  or  basin,  several  feet  below  the  surface  of 
the  water,  as  the  ice  simply  covers  the  basin,  and  the  water  flows 
to  the  pipe  beneath  it.  The  so-called  frazil  ice,  however — i.e.,  ice 
in  finely  divided  form — mixes  with  the  water  and  is  held  in  suspen- 
sion and  it  will,  therefore,  pass  through  the  pipes  to  the  turbines 
and  clog  them,  no  matter  how  far  below  the  surface  of  the  water 

4 


50          DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

the  pipe  may  be  placed.  A  large  forebay  or  settling  basin  at  the 
power-house  is  required  to  prevent  the  inflow  of  this  frazil  ice.  It 
slowly  floats  upward,  freezing  solid  at  the  surface,  and  in  this  way 
the  water  is  cleared. 

Accumulations  of  leaves  are  particularly  troublesome,  and  it 
is  difficult  to  clear  the  water  of  them.  Trash  racks,  such  as  de- 
scribed in  the  foregoing  chapter,  will  prevent  them  from  getting  to 
the  wheels,  but  the  racks  themselves  become  clogged  and  require 
continual  cleaning ;  in  some  cases  two  men  are  kept  busy  continu- 
ously clearing  the  racks. 

Specially  designed  forms  of  moving- chain  conveyors  which 
allow  the  water  to  pass  through  them,  but  catch  and  elevate  the 
leaves,  discharging  them  onto  a  platform  or  to  one  side  of  the  flume, 
have  been  used  with  success.  There  is  no  standard  device,  how- 
ever, for  this  purpose,  and  each  case  must  have  the  design  made 
to  suit  the  individual  conditions. 


CHAPTER  V. 

WATER-WHEELS. 

WATER-WHEELS  may  be  divided  into  three  classes,  viz.,  pressure 
turbines,  impulse  turbines,  and  Pelton  or  jet  wheels. 

The  pressure  turbine  consists  of  a  rotating  wheel  having  curved 
vanes  or  buckets  attached  to  its  periphery,  and  stationary  vanes 
which  serve  to  direct  the  flow  of  water  into  the  wheel  buckets.  The 
forms  of  the  guide  vanes  and  the  wheel  buckets  are  such  that  the 
water  enters  the  openings  without  appreciable  impact,  but  guided 
in  a  particular  direction  and  having  a  certain  velocity  of  flow. 
The  wheel  buckets  change  the  direction  of  flow  of  the  water,  and 
it  is  this  reaction,  due  to  changing  the  direction  of  motion  of  the 
mass  of  water,  that  produces  the  turning  effort  on  the  wheel.  There 
are  many  designs  for  forms  of  buckets,  and  most  of  the  success- 
ful ones  have  curvatures  in  two  planes  so  that  the  water  is  received 
at  the  level  of  one  plane  and  rejected  at  a  lower  plane,  its  direc- 
tion of  motion  continuously  changing  throughout  its  path  through 
the  wheel  buckets. 

The  wheel  and  guide  buckets  may  be  in  the  same  plane,  the 
stationary  guide  buckets  being  inside  the  periphery  of  the  wheel, 
the  water  being  received  through  a  central  opening  and  dis- 
charging radially  outward.  This  type  is  termed  the  outward-flow 
turbine.  If  the  guide  vanes  are  placed  above  the  wheel  so  that 
the  direction  of  flow  of  the  water  is  parallel  to  the  wheel  axis  and 
perpendicular  to  the  wheel,  it  is  called  a  parallel-flow  turbine. 
The  inward-flow  turbine  has  its  guide  buckets  outside  of  and 
surrounding  the  wheel,  the  water  passing  inwardly  and  radially 
toward  the  axis.  A  very  successful  form  of  wheel  or  runner  is 
shown  in  Fig.  27,  which  is  the  type  of  wheel  most  largely  used 

51 


52          DEVELOPMENT   AND    DISTRIBUTION   OF   WATER   POWER 

in  the  United  States.     It  combines  the  features  of  inward  and 
parallel  flow,  the  water  passing  to  the  wheel  inwardly  and  radially, 

and  being  discharged  from  it  down- 
wardly and  parallel  to  the  wheel 
shaft. 

Any  of  these  wheels  may  be  set 
with  their  axes  either  horizontal  or  ver- 
tical, provided  a  depth  of  not  less  than 
six  feet  of  water  is  obtainable  above 
the  upper,  surf  ace  of  the  wheel  when  set 
horizontally.  It  is  customary  to  em- 
ploy vertical  wheels  for  heads  of  less 
FlG  2?  than  twenty  feet,  although  horizontal 

wheels  have  been  placed  and  success- 
fully operated  under  heads  as  low  as  fourteen  feet. 

With  pressure  turbines  it  is  not  necessary  to  set  the  turbine 
down  at  the  level  of  the  tail  water  in  order  to  get  the  full  effect  of 
the  total  head.  As  before  mentioned  in  describing  power-house 
construction,  pressure  turbines  may  be  set  anywhere  from  two  to 
twenty  feet  above  the  level  on  the  tail  water  if  an  air-tight  draft  tube, 
leading  from  the  wheel  discharge  down  below  the  level  of  the  tail 
water,  be  provided.  This  is  due  to  the  fact  that  the  submerged 
end  of  the  tube  is  sealed,  and  the  falling  water  in  the  tube  from  the 
turbine  discharge  tends  to  create  a  vacuum  in  the  draft  tube, 
which  has  the  effect  of  sucking  the  water  through  the  turbine 
and  adding  a  pressure  to  the  inflowing  water  proportional  to  the 
vertical  height  of  the  draft  tube. 

The  usual  speed  of  pressure  turbines  is  such  as  to  give  a  periphe- 
ral velocity  of  the  wheel  equal  to  approximately  three-fourths  of 
the  spouting  velocity  of  the  water  under  the  head  applied.  Re- 
cently, however,  certain  high-speed  turbines  have  been  produced  in 
which  the  peripheral  speed  of  the  wheel  is  equal  to  90  to  95  per 
cent,  of  the  spouting  velocity  of  the  water.  The  spouting  velocity  in 

feet  per  second  is  equal  to  S\/  Head  in  feet. 

The  variation  in  the  power  of  the  wheel,  under  a  given  head, 


WATER-WHEELS 


53 


for  variations  in  load  is  effected  by  varying  the  amount  of  water 
admitted  to  the  guide  buckets  or  to  the  wheel  buckets.  There 
are  three  types  of  variable  gates,  viz.,  the  cylinder,  the  wicket, 
and  the  register  gate. 

Cylinder  gates  are  simply  sheet-iron  cylinders  which  surround 
the  stationary  guide  buckets.  These  cylinders  are  movable  in  a 
direction  parallel  to  the  wheel  axis.  In  one  extreme  position  the 
openings  to  the  guide  vanes  are  completely  covered;  in  the  other 
extreme  position  they  are  completely  uncovered.  As  the  cylinder 
moves  to  different  positions  between  these  extremes,  the  areas  of 
the  openings  are  correspondingly  varied. 

The  wicket  gate  is  arranged  as  shown  in  Figs.   28  and   29. 


FIG.  28. 


In  Fig.  28  is  shown  the  moving  mechanism,  while  in  Fig.  29  is  shown 
a  sectional  plan.  In  this  arrangement  the  guide  vanes  are  pivoted 
so  that  they  may  have  their  positions  shifted.  Each  vane  pivot 
has  a  crank  arm  attached  to  it,  and  an  iron  rod  is  connected  to  each 


54         DEVELOPMENT   AND   DISTRIBUTION  OF   WATER   POWER 

of  these  cranks.  The  iron  rods  all  have  their  ends  attached  to  a 
flat  central  ring  of  iron.  When  this  central  ring  is  rotated  through 
a  small  angle,  the  guide  vanes  are  caused  to  approach  toward  or 


-MOVING    GUIDES 

FIG.  29. 

recede  from  each  other,  thereby  varying  the  area  of  the  openings 
through  the  guide  vanes. 

The  register  gate  is  made  of  an  iron  cylinder  surrounding  the 
guide  vanes  and  having  a  series  of  openings  cut  into  it  the  size 
and  form  of  which  correspond  to  the  size  and  form  of  the  openings 
between  the  guide  vanes.  In  the  position  where  the  openings  in 
the  cylinder  correspond  exactly  with  those  between  the  guide  vanes, 
the  full  flow  of  water  passes  to  the  wheel.  If,  however,  the  cyl- 
inder be  rotated  through  a  small  angle  so  that  the  position  of  the 
openings  in  it  does  not  correspond  with  the  position  of  the  open- 
ings between  the  guide  vanes,  the  latter  will  be  closed  up  either 
partially  or  wholly,  depending  on  the  amount  of  rotation  of  the 


WATER-WHEELS  55 

cylinder,  and  thereby  the  flow  of  water  to  the  wheel  may  be  varied 
as  may  be  desired  from  zero  to  a  maximum. 

Of  these  gates  the  wicket  gate  is  most  used  and  is  probably 
the  most  satisfactory,  especially  when  the  gates  are  to  be  controlled 
by  an  automatic  governor.  The  cylinder  gate  is  also  a  good  form 
of  gate  for  automatic  governing.  The  register  gate  is  not  to  be 
recommended  except  when  the  water  is  free  from  sand  and  grit 
and  the  governing  is  to  be  done  by  hand,  as  it  is  subject  to  rapid 
wear  in  gritty  water,  and  the  friction  between  it  and  the  guide- 
vane  structure  is  too  great  to  admit  of  rapid  movement  with  ease. 

There  are  two  methods  of  supplying  water  to  pressure  tur- 
bines; one  is  to  set  the  wheel  in  a  large  chamber,  open  at  the  top, 
which  communicates  with  the  head  water  and  is  filled  up  to  prac- 
tically the  same  level  as  the  head  water,  completely  submerging 
the  wheel.  The  discharge  water  is  taken  from  the  wheel  through 
the  draft  tube,  which  passes  through  the  bottom  of  the  chamber 
and  is  sealed  in  the  bottom  so  that  none  of  the  water  can  pass  from 
the  chamber  through  this  opening;  the  only  possible  path  for  the 
water  being  through  the  turbine  and  out  by  the  draft  tube.  This 
is  called  an  open-penstock  setting.  Where  heads  are  low,  say  up  to 
thirty  feet,  this  is  the  best  possible  method  of  placing  a  turbine. 
Where  the  turbine  is  vertical,  the  shaft  projects  upwardly,  rising 
above  the  surface  of  the  water,  and  from  its  upper  end  power  may 
be  taken.  When  the  turbine  is  set  horizontally,  the  shaft  passes 
through  the  side  of  the  chamber,  a  water-tight  stuffing  box  be- 
ing placed  around  the  shaft  to  prevent  leakage.  Fig.  30  shows 
the  arrangement  of  a  pair  of  horizontal  turbines  set  in  an  open 
penstock,  the  shaft  passing  through  the  stuffing  box  in  the  side. 

Penstocks  may  be  made  in  any  manner  and  of  any  material 
which  will  be  water-tight.  In  some  cases  they  take  the  form  of 
large  square  wooden  boxes.  Usually,  however,  they  are  made  of  re- 
inforced concrete.  In  every  case  they  must  be  sufficiently  strength- 
ened and  braced  to  resist  the  water  pressure  which  tends  to  bulge 
the  walls  out  and  burst  them  apart.  Where  several  turbines  are 
installed,  it  is  advisable  to  separate  the  penstock  into  as  many 


56          DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

divisions  as  there  are  separate  turbine  units.  Normally,  the  di- 
vision walls  will  be  subject  to  no  bursting  stresses,  as  the  height 
of  water  is  the  same  on  either  side,  and  the  water  pressure  is  thus 


FIG.  30. 

neutralized.  If,  however,  it  becomes  necessary  to  inspect  any 
particular  turbine  or  make  repairs  on  it,  the  water  in  this  division 
of  the  penstock  must  be  drawn  off.  This  leaves  the  walls  of  the 
empty  division  subjected  to  the  pressure  of  the  water  from  the 
adjacent  compartments,  and  it  is  therefore  necessary  to  construct 
these  division  walls  with  the  same  strength  as  if  they  were  separate 
penstocks. 

The  other  method  of  setting  pressure  turbines  is  to  enclose 
each  unit  in  a  steel  casing,  into  which  water  is  conducted  by 
means  of  a  pipe  leading  to  the  head  water.  The  draft  tube  is 
taken  out  through  the  end  of  the  casing  or  down  through  the  bot- 
tom, depending  on  the  form  of  water-wheel  used.  This  method 
of  installing  has  certain  mechanical  advantages.  It  is  very  con- 
venient and  occupies  less  space  than  does  the  open  penstock,  and 


WATER-WHEELS 


57 


is  the  only  suitable  and  commercial  method  for  heads  above  thirty- 
five  feet.  The  speed  regulation  and  the  efficiency  attainable  are, 
however,  not  as  good  as  with  the  open-penstock  setting. 

The  pressure  of  the  water  against  the  wheel  is  principally 
radial,  but  there  is  considerable  pressure  also  exerted  in  a  direc- 
tion parallel  to  the  wheel  axis,  and  this  requires  that  turbines  be 
provided  with  thrust  bearings  to  take  this  longitudinal  pressure. 

In  order  to  neutralize  this  pressure  and  also  to  obtain  high 
rotative  speed  under  a  given  head,  it  is  customary  to  place  two  water- 
wheels  on  a  single  shaft,  each  wheel  having  half  the  power  that 
it  is  desired  for  the  unit  to  supply.  Since  the  longitudinal  press- 


FIG.  31. 

ures  act  in  opposite  directions,  they  neutralize  as  desired ;  and  as 
each  wheel  gives  only  half  the  power  required,  its  smaller  size 
gives  a  higher  rotative  speed.  When  set  in  an  open  penstock, 


58          DEVELOPMENT   AND   DISTRIBUTION    OF   WATER   POWER 

these  wheels  are  supported  by  a  draft  chest  which  rests  on  the 
bottom  of  the  penstock  and  to  which  the  draft  tube  is  attached 
that  takes  the  discharge  from  both  wheels.  Such  a  setting  is 
shown  in  Fig.  30.  Obviously,  a  pair  of  wheels  with  their  draft 
chest  instead  of  being  set  in  the  open  penstock  may  be  encased 
in  a  steel  shell  as  indicated  in  Fig.  31. 

In  many  cases  where  double  units  are  encased  in  a  cylindrical 
steel  penstock,  the  water,  instead  of  flowing  from  either  end  toward 
a  common  central  draft  chest,  flows  from  the  middle  toward  either 
end  and  discharges  through  two  draft  tubes  as  shown  in  Fig.  32. 
The  large,  ninety-degree  elbows  at  either  end  of  the  casing  are  called 
"quarter  turns,"  and  in  each  is  placed  a  stuffing  box  to  allow  the 


FIG.  32. 

turbine  shaft  to  pass  through.  This  form  possesses  several  ad- 
vantages over  the  central-draft-chest  arrangement.  Its  first  cost 
is  from  25  to  30  per  cent,  less  than  the  cost  of  central-draft-chest 
turbines  of  the  same  power,  its  efficiency  is  from  2  to  5  per  cent, 
greater,  and  it  may  be  supported  by  piers  or  pillars  directly  under 
the  turbine  casing  and  wheels.  Therefore  this  type  should  be 
used  whenever  possible. 


WATER-WHEELS  59 

The  efficiency  of  pressure  turbines  when  new  and  in  good 
condition  is  about  80  per  cent,  at  |  gate.  This  efficiency  usually 
falls  off  at  full  gate  and  below  |  gate.  Also,  in  the  course  of  time, 
the  buckets  become  worn  by  the  action  of  the  water,  grit,  and 
other  substances  which  are  carried  into  the  wheel,  and  both  the 
power  and  efficiency  are  reduced.  This  is  important  and  should 
be  borne  in  mind  when  deciding  on  the  size  of  wheel  necessary 
for  any  given  service.  At  least  12  J  per  cent,  excess  capacity  should 
be  allowed  to  admit  of  good  regulation  under  varying  loads  and 
to  compensate  for  this  reduction  in  power  which  takes  place  in 
the  course  of  time. 

Pressure  turbines  may  be  obtained  in  standard  designs  for 
heads  up  to  100  feet.  Specially  designed  wheels  for  heads  up  to 
1 60  feet  are  supplied  by  various  makers.  When  heads  are  greater 
than  1 60  feet  impulse  turbines  or  impulse  wheels  should  be 
used. 

Draught  tubes  should  be  proportioned  so  that  the  velocity  of 
the  water  in  them  is  about  five  feet  per  second  when  the  turbine  is 
developing  full  power.  When  the  velocity  is  less  than  two  feet 
per  second  the  vacuum  is  not  so  good  as  at  somewhat  higher  veloci- 
ties and  where  water-wheels  are  subjected  to  varying  loads  it  is 
possible  to  get  too  low  a  velocity  in  the  draught  tube  at  one-third  or 
one-half  gate.  Of  course,  if  wheels  are  designed  to  run  on  steady 
loads,  the  velocity  for  full  gate  may  be  somewhat  lower  than  the 
figure  given,  but  in  any  case  the  loss  of  head  in  a  draft  tube  even 
at  velocity  of  6  or  7  feet  per  second  is  practically  negligible,  and  as 
a  general  all-round  figure,  5  feet  per  second  is  about  the  best. 

Draught  tubes  should  taper  and  have  a  greater  diameter  at  the 
bottom  than  at  the  top.  The  diameter  at  the  bottom  should  be 
about  25  per  cent,  greater  than  the  diameter  at  the  top,  and  the  vel- 
ocity of  5  feet  per  second  should  be  taken  for  the  upper  or  small 
cross-section.  The  lower  end  of  the  tube  should  be  submerged 
at  least  8  inches  and  in  large  draught  tubes — say  8  feet  in  diam- 
eter and  above  at  the  bottom — they  should  be  submerged  not  less 
than  20  inches. 


60          DEVELOPMENT   AND    DISTRIBUTION   OF   WATER   POWER 

A  difficulty  that  frequently  confronts  the  designer  of  a  plant 
is  that  of  a  low  head  greatly  influenced  by  floods,  where  the  tail 
water  backs  up  in  time  of  flood  and  materially  reduces  the  effect- 
ive head.  Under  these  conditions  there  is  an  abundance  of 
water  available,  and  the  water-wheels  can  work  if  necessary  at  a 
low  efficiency.  The  power  and  speed  must  be  maintained  the  same 
as  when  the  normal  head  is  acting. 

Many  complicated  methods  of  involving  gears,  belts,  and  other 
devices  have  been  suggested.  It  is  the  author's  practice,  however, 
to  use  extra  turbine  wheels  or  runners  on  the  same  shaft,  sometimes 
fastened  solidly  on  and  sometimes  connected  or  disconnected 
by  means  of  a  jaw  clutch  coupling.  For  instance,  if  the  normal 
head  is  36  feet,  with  a  depth  of  6  feet  in  the  tail  race,  and  the 
flood  raises  the  depth  in  the  tail  race  to  18  feet,  making  the  net 
head  24  feet,  there  should  be  three  horizontal  turbines  on  a  single 
shaft.  Assume  the  power  to  be  developed  as  500  H.P.  Then  two 
of  the  turbines  running  at  full  gate  should  give  approximately 
575  H.P.  under  a  36-foot  head,  and  at  f  gate  they  will  give  500  H.P. 
Under  24  feet  head  at  full  gate,  they  will  give  only  312  H.P.  the 
power  of  a  turbine  being  not  proportional  to  the  head  but  to  the 

VHead3.  The  third  wheel,  therefore,  must  give  188  H.P.  under 
24  feet  head.  When  the  head  is  normal  this  third  wheel  is  idle,  its 
gates  are  closed,  and  it  merely  rotates  on  the  shaft  with  the  other 
wheels. 

The  speed  varies  as  the  square  root  of  the  head.  At  36  feet,  if  the 
speed  is  280  r.p.m.,at  24  feet  head,  it  will  tend  to  fall  to  229  r.p.m. 
'If  the  velocity  of  the  wheel  buckets  is  75  per  cent,  of  the  velocity 
of  the  water  at  36  feet  head,  and  a  5  per  cent,  fall  in  speed  at  high 
water  is  allowable,  the  rotative  speed  of  the  wheel  is -280 — 5  per 
cent.  =  266  r.p.m,  the  peripheral  velocity  of  the  wheel  will  be  about 
84  per  cent,  of  the  velocity  of  the  water  when  working  under  the 
lower  head.  The  two  main  wheels  therefore  should  work  with 
their  highest  efficiency  at  f  gate  with  a  peripheral  velocity  of  75 
per  cent,  of  the  velocity  of  the  water  under  36  feet  head  =  .  75  X  8  X 
=  36  ft.  per  second;  while  they  should  be  able  to  give  ap- 


WATER-WHEELS  6l 

proximately  their  full  proportional  power  when  running  at  85  per 
cent,  of  the  velocity  of  the  water,  and  the  third  wheel  should  be 
proportioned  to  work  under  the  lower  head. 

Sometimes  the  conditions  are  even  worse  than  the  above  case, 
and  it  may  become  necessary  to  install  two  turbines  on  a  single 
shaft,  one  of  which  gives  the  necessary  power  and  speed  at  the  nor- 
mal head,  the  other  giving  the  proper  power  and  speed  at  the  low 
head.  The  peripheral  velocity  of  the  smaller  wheel  for  the  high- 
head  service  may  be  greater  than  the  velocity  of  the  water  at  the 
low  head,  in  which  case  the  gates  of  this  wheel  must  be  completely 
shut  at  times  of  high  water,  as  it  not  only  would  not  assist  the  low- 
head  wheel,  but  would  be  a  drag  on  it,  using  up  instead  of  giving 
out  power. 

Another  method  of  arranging  turbines  to  compensate  for  varia- 
tion in  head  is  to  place  two  units  in  separate  steel  casings  or  pen- 
stocks, each  having  its  pipe  connection  to  head  water  and  its  draught 
tube,  both  wheels  being  on  the  same  shaft.  Additional  pipe  con- 
nections are  made  and  valves  put  in  at  proper  points,  which  allow 
the  shutting  off  of  one  draught  tube  at  the  bottom  and  turning  the 
water  from  the  closed  draught  tube  into  the  case  of  the  adjacent 
turbine.  A  valve  in  the  flume  or  pipe  line  leading  to  this  second 
unit,  cuts  off  the  water  from  the  source  of  supply.  With  both 
valves  open  each  turbine  receives  water  from  the  flume  and  dis- 
charges it  through  its  draught-tube,  and,  both  wheels  being  on  the 
same  shaft,  the  power  delivered  is  equal  to  the  combined  power 
of  the  two  wheels,  under  the  available  head.  This  is  the  opera- 
tion at  times  of  high  water  when  the  head  is  low  and  plenty  of 
water  is  available.  When  there  is  but  little  water  the  valves  are 
closed  and  the  water  then  passes  through  the  first  turbine,  into  the 
second,  and  out  through  the  draught  tube  of  the  second  wheel. 
Obviously,  the  speed  and  power  developed  by  these  units  under  a 
50  foot  head  with  200  cubic  feet  of  water  flowing  per  second  wrill 
be  the  same  as  the  speed  and  power  under  a  head  of  25  feet  and 
a  flow  of  400  cubic  feet  per  second.  At  intermediate  stages  of 
high  water,  between  the  normal  and  the  maximum,  partial  closing 


62          DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

of  the  valves  will  allow  corresponding  adjustment  of  the  units 
for  the  reduction  in  head  and  increase  in  the  volume  of  water. 

In  some  instances,  owing  to  very  low  head  or  want  of  room,  it 
becomes  necessary  to  use  vertical  turbines.  Any  pressure  turbine 
will  work  at  its  highest  efficiency  if  set  vertically.  The  difficulty, 
however,  is  in  transmitting  power  to  the  dynamo  which  is  usually 


FIG.  33. 

set  horizontally.  In  the  case  of  small  units,  this  may  be  done  by 
means  of  a  quarter-turn  belt  or  rope  drive,  but  this  is  not  feasible 
for  dynamos  of  above  100  kilo- watts.  Recently,  dynamos  have 
been  constructed  abroad  which  have  vertical  shafts  and  are  known 


WATER-WHEELS 


as  the  "umbrella"  type.  These  dynamos  may  be  set  directly 
over  the  water-wheels,  the  two  shafts  being  connected  together 
and  a  vertical,  direct-connected  unit  thus  produced.  Fig.  33 
shows  the  arrangement  of  such  units.  The  weight  of  the  turbine 
runner  and  of  the  rotating  part  of  the  dynamo,  together  with  the 
vertical  shaft,  form  a  rotating  mass  which  must  be  supported. 
Step  bearings  and  thrust-collar  devices  were  tried  for  a  time,  but 
their  excessive  friction  and  rapid  wear  made  the  horizontal  units 
far  preferable  when  conditions  allowed  their  use.  More  recently, 
hydraulic  thrust  bearings  having  but  little  friction  and  inappre- 
ciable wear  have  been  developed  and  are  in  successful  operation. 
The  ability,  however,  to  obtain  standard  dynamos  of  this  type 
in  various  sizes  and  speeds  is  so  limited  that  designs  for  vertical 
units  for  this  character  should  not  be  attempted  without  first  in- 
vestigating to  find  out  if  standard  patterns  are  available  for  the 
sizes  and  speeds  required. 

Many  vertical  turbines  driving  horizontal  dynamos  by  means 
of  bevel  gearing  have  been  installed  and  some  plants  of  this  type 
are  large  and  important.  The  author's  experience,  however, 
with  heavy  bevel  gears,  transmit- 
ting large  amounts  of  power,  has 
always  been  unsatisfactory.  It  is 
almost  impossible  to  keep  them  in 
good  condition,  they  absorb  a  large 
percentage  of  the  total  energy — 
often  as  high  as  fifteen  per  cent.— 
and  necessitate  constant  watching 
and  repairing.  No  such  drives 
should  ever  be  considered  except 
for  temporary  plants  or  in  loca- 
tions where  it  is  possible  to  use  no 
other  form  of  equipment.  Under 
heads  of  less  than  1 2  feet,  however, 
vertical  turbines  must  be  used  and  this  objectional  gearing  be- 
comes necessary.  Fig.  34  shows  a  vertical  turbine  driving  a 


FIG.  34. 


64          DEVELOPMENT    AND   DISTRIBUTION   OF   WATER   POWER 

horizontal  shaft  by  means  of  bevel  gears  and  the  arrangement 
is  quite  clear  from  the  figure. 

The  impulse  turbine  is  but  little  used  in  the  United  States, 
although  under  certain  conditions  it  is  advantageous  to  install 


FIG.  35. 

them.  They  differ  from  the  previously  described  pressure  turbines 
in  many  respects,  although  they  are  very  similar  in  their  action. 
The  wheels  themselves,  or  runners,  are  provided  with  a  series  of 
curved  buckets  which  much  resemble  the  form  of  buckets  used 
in  pressure  turbines.  Instead,  however,  of  water  being  admitted 
to  all  of  the  buckets,  and  the  whole  structure  solidly  filled,  the  water 
is  admitted  to  but  few  of  the  buckets,  being  carried  to  them  and 
given  its  initial  direction  by  one  or  more  nozzles.  Fig.  35  in- 
dicates the  general  arrangement  of  this  form  of  water-wheel,  a 
sectional  plan  being  shown.  The  water  passes  from  the  nozzle 
into  the  wheel  buckets  and  after  passing  through  the  latter  is  re- 
jected at  atmospheric  pressure.  Since  only  a  few  of  the  buckets 
have  water  passing  through  them— which  in  many  instances  does 
not  fill  the  bucket  space  completely — and  most  of  the  buckets  are 
entirely  empty,  it  is,  of  course,  impossible  to  use  a  draught  tube  and 
that  portion  of  the  head,  from  the  buckets  down  to  tail  water,  is  lost. 


WATER-WHEELS  65 

These  wheels,  when  provided  with  several  nozzles,  maintain 
their  efficiency  over  a  remarkable  range  of  load  change,  for  the 
reason  that  each  nozzle  acts  as  a  separate  unit  on  that  particular 
portion  of  the  wheel  covered  by  it,  and  regulation  for  load  variation 
is  obtained  by  shutting  off  one  nozzle  at  a  time,  which  does  not, 
in  any  wise,  affect  the  action  of  the  other  nozzle.  Also,  in  varying 
the  power  delivered  by  a  single  nozzle,  the  area  or  spread  of  the 
nozzle  is  diminished  and  this  simply  means  that  the  number  of 
buckets  acted  on  by  the  nozzle  is  reduced.  In  Fig.  35  is  shown 
a  movable  tongue  at  the  end  of  the  nozzle  which  varies  its  width 
with  load  changes. 

The  peripheral  speed  of  the  wheel  is  about  one-half  the  spout- 
ing velocity  of  the  water.  As  is  clear  from  its  characteristics, 
the  dimensions  of  the  wheel  may  be  made  nearly  anything  desired 
for  a  given  power  and  head. 

Where  heads  are  150  feet  and  up  to  600  feet,  these  wheels  give 


FIG.  36. 

excellent  results.     Under  lower  heads  the  pressure  turbine  is  pref- 
erable for  the  reasons  that  its  efficiency  at  or  near  its  rated  load, 
is  higher,  it  utilizes  the  total  head,  and  is  generally  less  expensive. 
5 


66          DEVELOPMENT   AND    DISTRIBUTION   OF   WATER   POWER 

The  Pelton  or  jet  impulse  wheels  are  suitable  for  heads  above 
150  feet.  They  have  the  advantages  of  high  efficiency,  simplicity, 
and  low  cost.  Fig.  36  shows  the  general  arrangement  of  this  form 
of  wheel.  The  water  emerges  from  the  nozzle  at  a  velocity  equal 
to  8\/head  and  strikes  against  the  wheel  buckets.  These  are 
formed  with  a  double  curvature  having  a  rib  in  the  middle  as  shown. 
The  water  strikes  against  the  sharp  edge  of  the  rib,  divides  in  two 
equal  parts,  half  going  into  one  side  of  the  bucket  and  half  into  the 
other.  The  water  impinges  against  the  bucket  surfaces  and  at 
the  same  time  sustains  a  change  in  the  direction  of  its  motion,  being 
discharged  by  bounding  back  practically  in  the  opposite  direction 
to  the  direction  of  flow  from  the  nozzle,  but  slightly  to  the  side  so 
that  the  reversed  water  does  not  encounter  the  incoming  nozzle 
flow.  The  object  of  this  design  is  to  completely  reverse  the  direc- 


FIG.  37. 

tion  of  flow  of  the  water  and  have  it  leave  the  wheel  at  practically 
zero  velocity,  thus  abstracting  all  the  kinetic  energy  from  the 
water. 

The  peripheral  velocity  of  the  wheel  is  practically  one-half  the 


WATER-WHEELS  67 

spouting  velocity  of  the  water,  and  the  efficiency  of  this  type  of  wheel 
is  often  as  high  as  eighty-five  per  cent.  In  a  wheel  of  given  size,  the 
power  may  be  increased  by  simply  increasing  the  number  of  nozzles, 
each  nozzle  adding  a  proportional  amount  of  power.  This  in- 
crease generally  is  not  to  be  carried  further  than  five  nozzles  to  any 
wheel,  a  certain  distance  between  nozzles  being  necessary  for  the 


?^^^s%^s?^%^>^^^r^:'^jX^^^££?-- 
FIG.  38. 

buckets  to  clear  themselves  of  water  received  from  one  nozzle 
before  receiving  water  from  the  next  adjacent  nozzle.  Fig.  37 
shows  a  triple  nozzle  to  apply  to  a  single  wheel.  When  it  is  de- 
sired to  obtain  a  high  rotative  speed  with  a  given  power,  two  or 
more  small  wheels  may  be  placed  on  one  shaft,  each  wheel  giving 
its  proportion  of  the  power  and  the  shaft  velocity  being  that  of  a 
small  single  wheel.  As  in  the  case  of  the  impulse  turbine,  the 
effective  head  is  only  that  from  the  level  of  the  head  water  to  the 
wheel,  that  portion  of  the  head  from  the  wheel  to  the  tail  water 
being  lost.  This  loss,  however,  with  the  high  heads  under  which 
these  wheels  work,  is  a  small  fraction  of  the  total  available  head 
and  in  such  cases  is  practically  negligible. 

The  wheels  are  usually  encased  in  an  iron  shell,  the  discharged 
water  falling  through  the  opening  in  the  bottom  of  the  case.  The 
power  is  varied  either  by  deflecting  the  nozzles  so  that  only  a  por- 
tion of  the  water  strikes  the  buckets,  or  by  the  so-called 'needle 
control.  In  this  latter  device  a  sharp-pointed,  conical-ended  rod 


68          DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

works  inside  the  nozzle  as  shown  in  Figs.  38  and  39,  Fig.  38  being 
a  sectional  view  and  Fig.  39  showing  the  nozzle  with  a  water  jet 
passing  from  it.  The  flow  of  water  is  varied  by  the  variation  in 
position  of  this  "needle. "  It  must,  however,  be  moved  with  com- 
parative slowness,  as  the  rapid  velocity  of  the  water  in  the  pipes 
leading  to  the  wheels  will  cause  a  destructive  shock  if  suddenly 
arrested.  Relief  valves  must  always  be  used  in  connection  with 


FIG.  39. 

needle  nozzles.  The  deflecting  jet,  while  it  performs  the  function 
of  regulation  satisfactorily,  is  very  wasteful  of  water  under  loads 
less  than  full  load,  as  the  flow  of  water  is  constant  whatever  the  load 
may  be 

Speed  Regulation  of  Water-Wheels. 

There  are  many  types  of  automatic  speed  governors  for  water- 
wheels,  and  improvements  in  these  mechanisms  are  being  made 
at  frequent  intervals.  It  is  possible  now  to  obtain  a  good  regulator 
at  a  reasonable  price.  To  describe  the  many  varieties  on  the 
market  and  their  methods  of  operation  would  be  superfluous  here. 


WATER-WHEELS  69 

It  may  be  said,  however,  that  they  all  use  some  form  of  fly-ball 
governor  which,  by  its  changes  in  position  with  speed  variations, 
sets  the  gate  opening  or  closing  mechanism  in  motion. 

These  governors  must  not  move  the  gates  too  rapidly  when 
the  water  is  conducted  to  the  turbine  through  long  pipes,  for  the 
reason  that  the  mass  of  water  in  a  pipe  moves  with  a  certain  ve- 
locity with  a  given  gate  opening  at  the  turbine,  and  if  the  gate  be 
closed  too  suddenly,  the  kinetic  energy  of  the  moving  column  of 
water  must  be  as  suddenly  dissipated.  The  only  way  that  this 
energy  may  be  dissipated  is  by  the  compression  of  the  water  itself 
and  distention  of  the  pipe.  Dangerous  pressures  may  thus  be 
produced  unless  the  pipe  is  provided  with  relief  valves  or  an  over- 
flow pipe. 

Conversely,  if  the  gate  be  opened  too  quickly,  the  column  of 
water  cannot  be  instantly  accelerated  and  it  tends  to  break  in  two, 
that  portion  nearest  the  wheel  running  into  the  increased  opening, 
separating  from  and  leaving  the  rest  of  the  water  in  the  pipe,  which 
cannot  so  quickly  attain  the  necessary  velocity.  As  a  result,  a 
space  is  left  in  the  pipe  which  is  a  vacuum  and  the  external  pressure 
of  the  air  tends  to  collapse  the  pipe.  Such  accidents  have  occurred 
and  should  be  provided  against  in  the  design  of  a  plant. 

A  peculiar  effect,  quite  opposite  from  that  desired,  also  attends 
rapid  gate  movement.  If  the  speed  of  the  turbine  decreases  and 
the  gate  be  suddenly  opened  to  cause  an  increase  in  speed,  the  wheel 
will  actually  decrease  its  speed  still  further,  for  a  few  seconds, 
due  to  the  decrease  in  pressure  as  above  described,  the  effect  of 
which  overbalances  the  effect  of  the  increased  gate  opening.  Also, 
if  the  speed  should  increase  and  the  gate  opening  be  suddenly 
decreased  to  bring  the  speed  back  to  its  normal  value,  the  wheel 
speed  will  increase  still  further,  due  to  the  increase  in  pressure 
set  up  by  the  suddenly  arrested  wrater  column,  the  effect  of  this 
increase  in  pressure  being  greater  than  the  effect  of  the  diminished 
gate  opening.  The  speed  will  then  gradually  fall  until  the  normal 
speed  is  attained,  several  seconds  being  sometimes  required  to 
produce  the  proper  speed  change.  Consequently,  the  governor 


7O          DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

should  move  the  gates  of  the  turbines  only  as  fast  as  the  column 
of  water  in  the  pipes  can  be  accelerated  or  retarded. 

The  foregoing  does  not  apply  to  turbines  set  in  open  penstocks 
nor  turbines  in  steel  casings  which  have  one  end  of  their  shells  set 
into  the  dam  or  bulkhead,  nor  do  these  remarks  apply  to  installa- 
tions where  the  conducting  pipes  are  only  a  few  feet  long — say  two 
or  three  times  their  diameter. 


PART  II 

ELECTRICAL  EQUIPMENT 


CHAPTER  VI. 

GENERAL  CONSIDERATIONS. 

THE  power  in  any  electrical  machine  or  transmission  line  is 
equal  to  the  product  of  volts  multiplied  by  amperes,  which  gives 
the  number  of  watts.  A  kilo-watt  (abbreviation  K.W.)  is  equal 
to  1000  watts.  A  horse-power  is  equal  to  746  watts,  hence  a  kilo- 
watt =1.34  H.P.  The  product  of  volts  ;  :  amperes  does  not 
represent  the  actual  power  delivered  by  an  alternating  current 
system,  except  under  certain  favorable  conditions,  the  power  being 
usually  less  than  the  volts  X  amperes  by  a  percentage  which  de- 
pends on  the  constants  of  the  system.  The  real  power  is  equal 
to  volts  X  amperes  X  <£,  in  which  <j)  is  a  factor  called  the  power 
jactor.  Only  when  the  power  factor  is  equal  to  i — as  it  is  in  all 
direct-current  systems  and  in  all  alternating-current  systems  in 
which  the  load  is  non-inductive,  such  as  incandescent  lamps, 
electrolytic  tanks,  synchronous  motors,  or  rotary  converters — is 
the  actual  power  equal  to  volts  X  amperes. 

The  power  factor  of  arc-lamp  circuits  is  about  0.82,  of  induc- 
tion motors  from  0.85  to  0.9,  according  to  construction  and  size. 
The  use  of  the  power  factor  in  calculations  will  be  shown  in  later 
discussions. 

There  are,  in  general,  two  systems,  between  which  the  de- 
signer of  a  power  station  may  choose — namely,  the  alternating  and 
the  continuous  or  direct  current. 

To  consider  the  origin,  interaction,  and  conditions  of  electric 

71 


72          DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

and  magnetic  phenomena  is  beyond  the  scope  and  intention  of  this 
work.  The  reader  who  desires  to  pursue  this  portion  of  the  sub- 
ject further,  is  referred  to  any  of  the  many  excellent  treatises  on 
electricity  and  magnetism  that  abound  in  all  languages  and  may 
be  obtained  in  nearly  any  locality.  It  therefore  suffices  to  say 
•here  that  continuous  current  flows  always  in  one  direction  through 
an  electric  circuit  or  machine,  and  is  the  same  kind  of  current  as 
is  given  out  by  an  electric  battery,  while  alternating  current  flows 
first  in  one  direction,  then  in  the  opposite  direction,  then  reverses 
again,  and  continues  to  change  its  direction  of  flow  as  long  as  the 
electricity  is  produced.  These  reversals  are  very  rapid  and  take 
place  at  a  rate  of  from  50  to  250  times  per  second,  or  from  3,000  to 
15,000  per  minute.  If  current  were  supplied  to  lamps  by  a  battery 
and  a  switch  were  connected  in  the  circuit  so  that  when  turned 
in  one  position  the  positive  pole  of  the  battery  is  connected  to  one 
of  the  wires  and  the  negative  pole  to  the  other  wire  leading  to  the 
lamps,  while  if  the  switch  be  turned  to  another  position  it  will 
connect  the  positive  pole  of  the  battery  to  the  second  wire  and  the 
negative  pole  to  the  first,  and  this  switch  were  rapidly  moved  back 
and  forth,  the  current  to  the  lamps  would  be  similar  to  the  alter- 
nating current  produced  by  alternating  dynamos.  Each  of  these 
systems  has  its  particular  place  in  the  art  and  in  some  cases  either 
is  suitable  for  a  given  kind  of  work. 

The  advantages  of  the  direct  current  are  as  follows:  Direct- 
current  dynamos  and  motors  may  be  obtained  in  a  greater  variety 
of  speeds  and  sizes  from  standard  patterns;  the  motors  will  give 
a  stronger  starting  torque  and  continue  to  run  under  heavier 
overloads  than  will  alternating-current  motors;  it  is  the  only  cur- 
rent which  will  operate  storage  batteries  and  in  connection  with 
them;  it,  only,  can  be  used  in  electroplating  and  electrolytic 
work  of  a  like  character;  its  phenomena  are  much  simpler,  easily 
calculated  and  understood  than  are  the  laws  which  apply  to  al- 
ternating currents.  It  has  the  disadvantage,  however,  of  requiring 
a  commutator  on  each  dynamo  or  motor,  with  brushes  bearing 
against  it  which  limits  the  voltage  of  the  machines  and  also,  when 


GENERAL   CONSIDERATIONS  73 

the  voltage  of  a  direct-current  system  is  once  fixed,  this  also  is  the 
voltage  of  all  the  distribution  lines  and  branches  with  their  rami- 
fications and  it  cannot  be  altered  except  by  the  use  of  electrical 
machinery. 

The  advantages  of  the  alternating  current  over  the  direct  cur- 
rent are:  The  dynamos  and  motors  are  simpler  in  their  construc- 
tion and  cost  less  than  direct-current  machines  of  similar  capacity; 
the  voltage  may  be  transformed  from  any  value  to  any  other  that 
may  be  desired  by  the  use  of  simple  and  low-priced  static  trans- 
formers which  have  no  moving  parts  and  consist  merely  of  two 
coils  of  wire  wound  on  an  iron  core.  Furthermore,  in  the  case  of 
three-phase  alternating  current,  the  amount  of  wire  required  to  trans- 
mit a  given  power  over  a  given  distance  is  twenty-five  per  cent,  less 
than  the  amount  required  for  a  similar  direct-current  transmission. 
As  will  be  shown  later,  the  use  of  high  voltages  is  necessary  when 
electrical  energy  is  to  be  transmitted  over  long  distances,  and,  in 
even  as  short  a  distance  as  one  mile,  the  proper  voltage  is  greater 
than  that  which  is  produced  by  any  standard  direct-current  machine 
for  power  sen-ice  that  is  made  in  the  United  States.  Electric 
railways  are  best  operated  by  550  volts  direct  current,  and  the 
standard  available  railway  equipments  are  all  for  this  voltage. 
Therefore,  in  general,  the  system  chosen  should  be  direct  current 
when  the  distance  of  transmission  is  short  and  the  power  is  to  be 
used  on  electric  railways,  for  electrolytic  work,  or  for  supplying 
power  to  mills  and  factories  where  the  speed  of  the  machinery  has 
to  be  varied  through  a  wide  range  and  the  initial  starting  effort 
of  the  motors  must  be  high.  In  cases  wrhere  the  conditions  require 
the  use  of  alternating  current,  but  some  direct-current  is  needed, 
an  alternating  current  system  should  be  installed  and  the  small 
proportion  of  direct  current  needed  may  be  obtained  by  using  a 
rotary  converter  or  a  motor  generator  set,  which  latter  is  made 
up  of  an  alternating  current  motor  driving  a  direct-current  dynamo. 

In  every  alternating-current  power  station  there  are  also  placed 
small  direct-current  dynamos,  called  exciters,  the  current  from 
which  is  used  to  magnetize  the  field  magnets  of  the  alternating- 


74          DEVELOPMENT   AND    DISTRIBUTION   OF   WATER   POWER 

current  generators.  In  many  instances  the  capacity  of  these 
exciters  is  made  great  enough  to  supply  not  only  the  needed  field 
exciting  current  but  to  furnish  some  additional  current  for  other 
purposes  as  well.  In  a  power  station,  recently  designed  by  the 
author,  the  exciters  installed  are  large  enough  to  furnish  current 
for  lighting  the  power  station  and  certain  adjacent  buildings,  in 
addition  to  supplying  the  necessary  field  excitation  to  the  alter- 
nating-current dynamos.  The  reason  for  the  adoption  of  this 
method  of  lighting  was  that  the  voltage  of  the  power  dynamos  was 
subject  to  considerable  variation  which  would  have  manifested 
itself  by  variation  in  the  illumination  if  the  lamps  had  been  sup- 
plied from  these  machines. 

In  deciding  on  the  size  and  type  of  dynamo  to  be  used  it  must 
be  remembered  that  the  lower  the  speed  at  which  it  runs  the  greater 
will  be  its  cost  for  a  given  capacity.  For  this  reason  it  is  fre- 
quently cheaper  to  make  use  of  a  high-priced  turbine  which  runs  at 
a  high  speed  than  to  purchase  a  lower-priced  low-speed  turbine 
when  the  machines  are  to  be  directly  connected  together.  Thus,  a 
single  turbine  of  500  H.P.  operating  under  a  50  foot  head  will  cost 
about  $1,800  and  will  run  at  about  275  r.p.m.  Two  250  H.P. 
turbines  on  a  single  shaft  will  cost  $2,100  and  run  at  450  r.p.m. 
The  cost  of  the  375  K.W.  alternating- current  dynamo,  running  at 
the  speed  of  the  single  wheel,  will  cost  $4,800,  making  the  cost 
of  the  low-speed  unit  complete  $6,600,  while  a  dynamo  of  similar 
capacity  at  the  higher  speed  will  cost  $3,800,  making  the  cost  of 
the  high-speed  unit  complete  $5,900,  so  that  by  using  the  higher- 
price  turbine  a  lower  cost  generating  unit  is  obtained. 

The  size  of  the  dynamo  to  be  used  in  a  power  station  is  gen- 
erally obtained  as  follows:  the  gross  horse-power  to  be  developed 
is  computed  by  the  methods  given  in  a  previous  chapter.  Eighty 
per  cent,  of  this  is  available  at  the  turbine  shaft.  The  dynamo  effi- 
ciency, including  the  power  required  to  operate  the  exciter,  is  about 
92  per  cent.  The  total  dynamo  power,  therefore,  is  92  per  cent,  of 
80  per  cent,  or  73.6  per  cent,  of  the  gross  available  power.  The 
total  dynamo  power  thus  found  should  be  divided  among  several 


GENERAL   CONSIDERATIONS  75 

machines,  and,  where  possible,  the  number  of  the  machines  should 
not  be  less  than  four  nor  should  the  number  exceed  ten.  When 
as  many  as  four  machines  are  used,  if  one  should  break  down  the 
other  three,  working  at  20  to  25  per  cent,  overload,  would  deliver 
nearly  the  full  power  of  the  station. 

The  water-wheels  should  each  have  a  capacity  15  to  20  per 
cent,  greater  than  the  power  required  to  drive  its  dynamo.  It 
sometimes  is  better  to  drive  dynamos  by  belts  from  pulleys  on  the 
water-wheel  shaft,  or  in  large  sizes,  to  use  rope  drives,  than  to 
connect  directly  the  two  shafts.  This  is  frequently  true  in  the  case 
of  low  heads  where  turbine  speeds  are  so  low  that  the  high  cost 
of  the  generators  would  make  the  investment  for  direct-connected 
units  excessive.  When  belted  units  are  installed,  however,  the 
distance  required  between  the  centres  of  the  two  shafts,  in  order  to 
give  sufficient  length  to  the  belt,  increases  the  size  of  the  power- 
house and  likewise  its  cost.  Before  deciding,  therefore,  on  whether 
or  not  it  is  best  to  use  belted  or  direct-connected  units,  computa- 
tions should  be  made  showing  the  comparative  total  cost  of  the 
units,  plus  power-house  for  each  case.  In  making  this  computa- 
tion the  item  of  belting  should  not  be  omitted  as  high-grade,  double 
leather  belts  cost  about  16  cts.  per  foot  for  each  inch  in  width. 
Thus  a  3O-inch  belt  will  cost  30  X  16  =  $4. 80  per  foot  length,  and 
with  25  feet  between  centres  and  usual  size  pulleys  about  60  feet 
of  belting  are  required,  costing  $288.00.  The  extra  cost  of  the 
pulleys  should  also  be  included. 


CHAPTER  VII. 
ALTERNATING- CURRENT  DYNAMOS. 

THERE  are  many  kinds  of  alternating-current  dynamos,  but 
at  the  present  day  the  only  sorts  which  are  in  general  use  are  the 
revolving  field  and  the  inductor  types.  The  inductor,  while  an 
excellent  form  of  machine,  is  being  almost  entirely  supplanted  by 
the  revolving-field  machines,  owing  to  the  lower  cost  of  manufac- 
ture of  the  latter. 

Inductor  dynamos  are  constructed  as  indicated  in  Figs.  40 
and  41.  Fig.  40  shows  the  complete  dynamo,  while  Fig.  41 
shows  the  inductor  with  its  central  magnetizing  coil.  The  arma- 
ture winding  is  placed  in  slots  or  grooves  cut  on  the  inner  surface 
of  the  stationary  ring  of  laminated  iron  which  surrounds  the  in- 
ductor and  is  held  in  position  by  the  external  iron  frame  of  the 
dynamo.  The  inductor  itself  consists  of  a  wheel,  having  mounted 
on  its  rim  a  number  of  masses  of  laminated  iron  arranged  in  pairs, 
side  by  side  and  equally  spaced  around  the  circumference  of  the 
inductor  wheel  as  indicated  in  Fig.  41.  Encircling  the  rotor, 
but  not  in  contact  with  it,  is  the  circular  channel  carrying  the  mag- 
netizing coil,  which  corresponds  to  the  field  winding  in  other 
forms  of  dynamos.  This  single  coil,  which  is  stationary  and  does 
not  rotate,  magnetizes  all  of  the  rotating  masses  of  iron  on  the  in- 
ductor wheel.  As  is  obvious  from  the  figure,  all  of  the  masses  of 
iron  on  one  side  of  the  coil  are  magnetized  as  north  poles,  while 
those  on  the  other  side  of  the  coil  are  magnetized  as  south  poles, 
the  magnetic  circuit  being  completed  through  the  laminated  iron 
ring  encircling  the  inductor,  which  is  separated  from  the  mag- 
netized portions  of  the  inductor  by  only  a  small  air  gap.  There 
is  no  moving  wire  whatever  in  this  form  of  dynamo  and  consequent- 

76 


ALTERNATING-CURRENT   DYNAMOS 


77 


ly  it  is  not  necessary  to  use  collector  rings  and  brushes,  all  con- 
nections to  the  field  and  armature  windings  being  made  in  the  or- 
dinary manner  as  they  are  both  stationary.  This  description  and 
the  figures  apply  of  course  to  but  one  particular  type,  but  there  are 


FIG.  40. 

several  forms  of  inductor  machines  which  have  no  moving  wire,  and 
which  work  on  the  principles  outlined  above. 

Dynamos  of  this  kind  are  durable,  usually  of  high  efficiency, 
and  they  are  in  every  respect  satisfactorily  operating  machines. 
Their  one  disadvantage  is  their  high  cost  of  manufacture. 

The  revolving-field  alternator  is  similar  to  the  inductor  alter- 
nator in  that  its  armature  winding  is  stationary,  the  coils  being 


78 


DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 


embedded  in  slots  made  in  the  outside  ring  of  laminated  iron. 
The  rotating  part  consists  of  a  wheel  having  fastened  to  its  periph- 
ery a  number  of  short  field-poles,  equally  spaced  around  the 
circumference  and  projecting  radially  outward  towards  the  en- 
circling stationary  iron  ring,  carrying  the  armature  winding. 
Each  of  these  field  poles  is  surrounded  by  a  field  winding  and 
the  outer  ends  of  the  poles  approach  very  near  to  the  inner  surface 
of  the  stationary  iron  ring,  a  small  air  gap  separating  them.  Figs. 


FIG.  41. 

42  and  43  show  the  stationary  ring  carrying  the  armature 
windings  and  the  rotating  field  member  (or  rotor)  respectively, 
of  a  standard  machine  of  this  type.  The  complete  machine  is 
shown  in  Fig.  44.  The  connections  to  the  armature  are  made 
without  collectors  or  brushes.  The  field-magnet  windings  all 
rotate  and  it  therefore  is  necessary  to  transmit  current  to  them 
through  collector  rings,  having  brushes  bearing  on  them.  The 


ALTERNATING-CURRENT    DYNAMOS 


79 


field  current,  however,  is  always  very  small  and  the  voltage  low 
as  compared  with  the  output  from  the  armature,  and,  therefore, 
the  size  of  the  brushes  and  collector  rings  is  small,  and  there  is  no 


FIG.  42. 

difficulty  whatever  in  their  operation.  This  type  of  machine 
may  be  constructed  at  a  low  cost  and  they  are  so  thoroughly 
satisfactory  that  they  are  almost  exclusively  used  in  the  United 
States  at  the  present  time. 

Both  the  inductor  and  rotating-field  machines  have  .one  ad- 
vantage in  common,  viz.,  the  stationary  armature  winding  and 
direct  connection  from  it  to  the  outgoing  transmission  line  without 


8o 


DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 


the  use  of  collector  rings  and  brushes.  This  admits  of  insulating 
the  armature  winding  to  the  same  degree  that  a  transformer  wind- 
ing may  be  insulated,  and,  in  consequence,  dynamos  may  be  wound 
for  extraordinarily  high  potentials,  it  being  easy  to  obtain  machines 
in  many  standard  sizes  which  deliver  6,600  volts  and  a  few  have 
been  made  which  give  13,000  volts.  For  comparatively  short 

transmissions — say  up  to  fifteen 
miles — these  potentials  are  high 
enough  and  the  use  of  step- up 
transformers  and  the  expense  of 
purchasing  them  are  avoided. 

Practically  all  generators  used 
for  power  transmission  are  for 
three-phase  currents,  the  three- 
phase  system  now  being  standard 
for  this  work,  as  the  costs  of  the 
generators  and  of  the  line  copper 
are  less  than  for  any  other  sys- 
tem. There  are  two  frequencies 
which  also  have  become  standard, 
viz.,  60  cycles  and  25  cycles  per 
second.  The  higher  frequency  is 
suitable  for  supplying  current  to 
motors  and  to  lamps,  either  incandescent  or  arc.  It,  however, 
has  the  disadvantage  of  giving  a  higher  line  drop  and  poorer  regu- 
lation on  long  transmission  lines  than  does  the  lower  frequency, 
and,  furthermore,  it  is  difficult  to  operate  rotary  converters  at  60 
cycles.  Generally,  the  costs  of  transformers,  dynamos,  and  mo- 
tors are  somewhat  less  for  the  frequency  of  60  cycles  than  for  25. 
The  frequency  of  any  dynamo  is  equal  to  the  number  of  poles  X 
revolutions  per  minute  -r-  1 20,  and  conversely  the  number  of  poles 
in  a  machine  are  equal  to  alternations  per  minute  -r-  revolutions 
per  minute  or  equal  to  cycles  per  second  X  120  -=-  revolutions  per 
minute. 

The  lower  frequency  has  the  disadvantage  of  being  unsuitable 


FIG.  43. 


ALTERNATING-CURRENT   DYNAMOS 


8l 


for  lighting,  and  dynamos,  motors  and  transformers  cost  slightly 
more  than  those  for  60  cycles.  The  inductive  drop  on  a  long 
transmission  line,  however,  is  less  and  rotary  converters  operate 
with  ease  at  this  frequency.  Therefore,  in  choosing  the  frequency, 


FIG.  44. 

the  character  of  the  load  is  the  determining  factor.  If  the  line  is 
short  and  there  is  considerable  lighting  load  and  but  a  small 
amount  of  direct  current  is  required,  60  cycles  is  the  proper  fre- 
quency. The  direct  current  may  be  obtained  by  using  small 
rotary  converters  which  can  be  made  to  work  fairly  well  at  60 
cycles,  or  by  using  direct-current  generators  driven  by  alternating- 
current  motors.  If  the  line  is  long — 60  miles  or  more — and  a 
large  amount  of  direct  current  is  required  at  the  distributing  end 
of  the  line  and  the  lighting  load  is  comparatively  small,  25  cycles 
6 


ALTERNATING- CURRENT  DYNAMOS  83 

is  the  better  frequency.  In  any  case,  where  the  larger  part  of  the 
load  is  to  be  in  the  form  of  direct  current,  as  for  instance  an  elec- 
tric railway  system,  the  low  frequency  should  always  be  adopted, 
in  order  that  rotary  converters  may  be  used  and  made  to  work 
satisfactorily  in  parallel. 

These  factors  may  vary  in  such  a  manner  as  to  render  a  de- 
cision somewhat  difficult,  and  the  only  thing  to  do  in  such  a  case 
is  to  investigate  carefully  various  operating  plants  supplying  ser- 
vice somewhat  similar  to  that  contemplated  in  the  prospective 
plant,  and  profit  by  the  experience  of  others. 

Dynamos  are  made  in  various  efficiencies,  the  efficiency  de- 
pending somewhat  on  the  cost.  High-efficiency  machines  require 
more  iron  and  copper  to  construct  than  do  those  of  low  efficiency. 
The  word  efficiency  is  used  here  in  its  technical  sense  and  is  equal 
to  the  power  which  is  delivered  by  a  dynamo  divided  by  the  power 
which  must  be  applied  to  the  dynamo  shaft  in  order  to  obtain  the 
delivered  power.  In  a  1,000  K.W.  machine  the  efficiency  may  be 
from  92  to  96  per  cent.  This  means  that  from  4  to  8  per  cent,  of 
the  total  power  furnished  is  lost  in  the  dynamo,  which  loss  goes 
into  the  form  of  heat,  the  temperature  of  the  copper  and  the  iron 
being  raised  above  that  of  the  surrounding  atmosphere  and  a  con- 
stant radiation  thus  produced,  which  dissipates  a  certain  propor- 
tion of  the  total  energy.  Some  of  this  lost  power  is  also  used  up 
in  driving  the  small  exciter  dynamo  which  furnishes  current  to  the 
field  magnets.  The  energy  thus  lost  in  a  1,000  K.W.  dynamo  will 
be  from  40  to  80  K.W.  or  from  54  to  108  H.P.  Whether  it  is 
better  to  pay  a  higher  price  for  the  dynamo  of  higher  efficiency 
or  not,  depends  entirely  on  the  conditions  that  obtain  in  any  par- 
ticular plant.  If  the  water  power  is  abundant  and  greater  than 
will  ever  be  used  in  the  locality  where  the  development  is  made, 
the  low-efficiency  machine  should  be  used.  If,  however,  the  water 
power  is  limited  and  the  value  of  power  high,  the  high-efficiency 
dynamo  should  be  installed.  Taking  the  case  of  the  1,000  K.W. 
dynamo  above,  at  the  two  extremes  given,  the  salable  power  from 
the  high-efficiency  dynamo  is  54  H.P.  in  excess  of  that  from  the 


84          DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

low-efficiency  machine,  the  water  power  being  the  same  in  each 
case.  If  this  power  is  salable  at  $15.00  per  annum  per  H.P.,  the 
income  that  may  be  derived  from  the  high-efficiency  dynamo  is 
$810.00  per  annum  more  than  the  income  obtainable  if  the  low- 
efficiency  machine  be  used.  Assuming  that  all  increase  in  ex- 
penditure above  that  absolutely  necessary  to  get  the  plant  in  com- 
mission must  return  15  per  cent,  on  the  added  investment,  $5,400.00 
more  could  be  paid  for  the  high-efficiency  machine  than  for  the  one 
having  the  low  efficiency.  The  actual  excess  cost  would  not  ex- 
ceed $1,000.00,  so  it  is  evident  that  the  high-efficiency  machine  is 
the  better  paying  one.  This  same  reasoning  applies  also  to  tur- 
bines. These  considerations  are  of  great  importance  in  every  case 
where  power  is  limited  and  should  receive  careful  consideration. 

Another  vital  question  is  that  of  regulation.  This  is  denned 
as  the  percentage  change  in  the  voltage  of  a  dynamo  between  the 
limits  of  full-load  current  and  no  load,  the  field  excitation  and 
speed  remaining  unchanged.  All  variations  in  voltage  at  the  dy- 
namo will  be  transmitted  over  the  line  to  the  points  of  distribution 
and,  in  the  case  of  rotary  converters,  cause  a  corresponding  change 
in  the  direct-current  voltage  and  thereby  produce  fluctuations  in 
the  direct-current  service.  Also,  where  lights  are  fed  from  the 
line  or  from  rotary  converters  the  fluctuation  in  brilliancy  with 
even  small  changes  in  the  voltage  are  marked  and  the  service  is 
unsatisfactory. 

On  the  other  hand,  if  the  load  be  entirely  of  motors,  a  greater 
voltage  change  is  allowable  and  good  regulation  not  so  necessary. 

Dynamos  having  high  efficiency  always  have  good  regulation 
also,  that  is,  the  change  in  voltage  with  change  in  load  is  small. 

The  best  machines  have  a  regulation  of  6  per  cent,  on  non- 
inductive  load  or  8  per  cent,  on  an  inductive  load  of  85  per  cent, 
power  factor,  while  some  standard  machines  have  a  regulation  of 
14  per  cent,  on  non-inductive  and  18  or  20  per  cent,  on  inductive 
loads. 

The  regulation  of  generators  for  long  transmissions  should  be 
as  good  as  possible  for  the  reason  that  the  drop  in  potential  from 


ALTERNATING-CURRENT   DYNAMOS  85 

the  generator  to  the  receiving  motors  or  other  translating  devices 
is  the  sum  of  the  drops  in  the  generator  and  in  the  line,  and  both 
of  these  increase  with  increase  in  current.  Generally,  the  load  on 
a  transmission  plant,  though  subject  to  variation,  does  not  fluctuate 
sharply,  the  changes  in  load  taking  place  gradually,  and  the  line 
and  generator  drops  may  be  compensated  for  by  variation  in  the 
generator-field  excitation.  Therefore,  the  character  of  the  load 
influences  the  degree  of  regulation  necessary,  sharply  fluctuating 
loads  requiring  a  better  regulation  of  line  and  generators  than  grad- 
ually changing  loads  which  are  subject  to  rheostatic  control  of  the 
exciter. 

At  present,  automatic  voltage  regulators  can  be  purchased  in 
the  open  market  at  reasonable  prices.  These  automatically 
adjust  the  field  excitation  to  give  a  constant  voltage  at  the  dynamo 
terminals  no  matter  what  the  inherent  regulation  of  the  machine 
itself  may  be.  They  may  be  adjusted  to  cause  an  increase  in  volt- 
age with  increase  in  current,  thereby  compensating  for  the  in- 
creased line  drop,  the  effect  being  practically  similar  to  that  of  an 
over-compounded  direct-current  dynamo.  They  are  independ- 
ent mechanisms  and  may  be  applied  to  any  generator  and,  in  the 
case  of  dynamos  of  200  K.W.  and  above,  it  is  usually  cheaper  to 
install  a  dynamo  having  a  low  regulation  factor,  and  purchase  the 
voltage  regulator  to  work  with  it,  than  to  pay  the  higher  price  for 
the  dynamo  having  a  better  regulation.  Furthermore,  the  oper- 
ation of  the  automatically  controlled  dynamo  is  superior  to  that 
of  one  having  the  best  possible  inherent  regulation  and  not  so 
controlled. 

The  speed  regulation  of  the  units  may  be  allowed  to  fluctuate 
somewhat,  if  the  voltage  is  automatically  maintained  constant, 
provided  current  is  not  furnished  to  any  synchronous  motors  or 
rotary  converters.  Since  all  synchronous  machinery  operates 
at  exactly  the  same  electrical  speed — i.e.,  the  time  of  rotation  from 
one  pole  to  the  next  adjacent  pole — as  that  of  the  generator,  and 
this  relation  is  as  rigidly  fixed  as  if  the  machines  were  geared  to- 
gether, any  change  in  generator  speed  must  be  accompanied  by  an 


86          DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

exactly  corresponding  change  in  the  speed  of  the  synchronous 
machine.  Therefore,  a  sudden  change  in  the  dynamo  speed  may 
result  in  the  synchronous  machine  running  out  of  step  with  the 
generator  alternations,  due  to  the  fact  that  the  fly-wheel  effect  of 
the  rotating  parts  of  the  synchronous  machines  will  prevent  them 
from  suddenly  speeding  up  or  slowing  down  to  conform  with  the 
sudden  changes  in  generator  speed.  As  a  result,  the  synchronous 
machines  will  slow  down  and  stop  and,  during  the  period  of  stop- 
ping, heavy  surging  of  current  will  take  place  on  the  line  which, 
for  the  time,  will  destroy  the  regulation  and  may  set  up  injurious 
voltages  due  to  inductive  or  resonance  effects.  Therefore,  the  pro- 
vision for  speed  regulation  must  be  very  much  more  elaborate 
when  synchronous  machines  are  to  be  operated  than  when  the 
energy  is  supplied  only  to  lights  and  induction  motors.  Of 
course,  gradual  changes  in  speed  do  no  harm  if  they  take  place 
slowly  enough  to  allow  the  speed  of  the  synchronous  machines  to 
follow  such  variations.  Frequently,  heavy  fly-wheels  are  placed 
on  the  turbine  shafts  and  these,  when  properly  proportioned  for  the 
speed  and  probable  maximum  load  changes,  are  effectual  in  pre- 
vention of  sudden  speed  fluctuation. 

The  required  capacity  of  the  dynamos  depends  not  only  on 
the  power  to  be  delivered  but  the  character  of  the  load.  If  the 
current  is  all  used  by  incandescent  lamps  or  synchronous  ma- 
chines, the  power  factor  will  be  approximately  equal  to  i  and  the 
dynamo  capacity,  in  kilo-watts,  will  be  equal  to  the  actual  power 
requirement  of  the  lamps  and  machines  supplied,  plus  the  loss  in 
the  line.  If,  however,  the  energy  is  supplied  to  induction  motors 
or  arc  lamps,  the  power  factor  will  then  be  considerably  less  than 
i,  its  value  being  usually  somewhere  between  0.8  and  0.9. 

The  power  factor  may  be  defined,  in  plain  words,  as  the  ratio 
of  the  actual  energy  supplied,  to  the  required  generator  capacity. 
That  is,  the  load  in  kilo-watts  divided  by  the  power  factor  is 
equal  to  the  required  K.W.  capacity  of  the  generator.  There- 
fore, if  the  K.W.  requirement  of  the  load  is  equal  to  1,000  K.W. 
and  the  power  factor  is  0.8,  the  capacity  of  the  generator  must  be 


ALTERNATING-CURRENT   DYNAMOS  87 

1,000  -T-  0.8,  equal  to  1,250  apparent  K.W.  If  the  generator 
voltage  is  1,000  volts,  the  current — assuming  a  single-phase  trans- 
mission— will  be  1,250  amperes.  The  actual  energy  supplied, 
however,  is  only  1,000  K.W.,  and  although  the  generator  may 
apparently  deliver  1,250  K.W.,the  actual  load  on  the  water-wheel 
is  only  i,oooK.  W.,  plus  the  losses  in  the  generator.  Under  these 
conditions  it  is  clear  that  the  energy  supplied  is  equal  to  the  prod- 
uct of  volts  X  amperes  X  power  factor.  The  product  of  volts  X 
amperes  is  called  the  apparent  watts,  and  owing  to  the  fact  that  the 
power  factor  may  vary,  so  that  the  actual  kilo-watts  supplied  by  a 
given  current  under  a  given  voltage  may  correspondingly  vary,  it 
has  become  customary  to  express  the  capacity  of  alternating  cur- 
rent generators  in  kilo-volt-amperes  (abbreviated  K.V.A.)  in- 
stead of  kilo-watts.  It  is  obvious,  therefore,  that  where  the  power 
factor  is  0.8,  the  size  of  the  generator  must  be  25  per  cent,  greater 
than  the  computed  load  requirements  would  indicate,  or  if  the 
power  factor  were  0.9  the  generator  would  have  to  be  of  n  per 
cent,  greater  capacity  than  the  load  demand  shows.  This  increase 
in  generator  size  does  not  require  a  corresponding  increase  in  the 
power  of  the  turbine,  because  with  a  power  factor,  for  instance, 
of  0.8  the  generator  may  deliver  apparently  1,250  K.W.  while 
the  actual  energy  output  will  be  only  0.8  times  this  or  1,000  K.W. 
In  other  words,  a  power  factor  requires  an  increase  of  current  to 
deliver  a  given  amount  of  energy  and  the  dynamo  must  be  large 
enough  to  furnish  this  increased  current  without  overheating. 

When  current  is  passed  through  any  conductor,  heat  is  liberated 
by  an  amount  proportional  to  the  resistance  in  ohms  of  the  conduc- 
tor and  to  the  square  of  the  current  in  amperes,  or  H  =  I2  R.  Also 
with  repeated  reversals  of  magnetization,  such  as  rapidly  occur  in 
electric  generators,  a  certain  amount  of  energy  is  absorbed  propor- 
tional to  the  number  of  reversals,  the  mass  of  the  iron  affected,  and 
the  magnetic  density.  This  absorbed  energy  also  manifests  it- 
self in  the  form  of  heat.  Both  of  these  conditions  for  the  genera- 
tion of  heat  are  present  in  every  electric  generator  and  as  a  result 
the  temperature  of  a  dynamo  will  rise  above  that  of  the  surround- 


88          DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

ing  air  until  it  attains  a  value  such  that  it  can  radiate  the  heat  as 
rapidly  as  it  is  produced.  Since  dynamos  are  made  with  certain 
materials  in  them,  such  as  cotton  and  fibre,  which  are  used  for  in- 
sulating purposes  and  which  deteriorate  rapidly  under  the  in- 
fluence of  high  temperatures,  they  should  be  designed  and  pro- 
portioned so  that  the  rise  in  temperature  shall  not  be  very  great. 
The  greater  the  amounts  of  iron  and  copper  in  a  dynamo  or  motor 
per  K.W.  of  output,  the  smaller  will  be  the  temperature  rise.  Other 
things  being  equal,  the  smallness  of  the  temperature  rise  is  a  meas- 
ure of  the  excellence  and  value  of  the  dynamo.  The  same  factors 
in  design  which  produce  high  efficiency  and  good  regulation  also 
give  a  small  temperature  rise.  In  fact,  since  the  efficiency  measures 
the  energy  lost  in  the  generator  and  this  energy  loss  is  continu- 
ously dissipated  in  the  form  of  heat,  the  efficiency  practically 
measures  the  temperature  rise,  modified,  of  course,  by  certain 
characteristics  of  design  to  ventilate  the  heated  portions.  It  has 
been  found  that  about  165°  F.  or  74°  C.  is  about  the  maxi- 
mum temperature  that  insulating  materials  will  stand  continuously 
without  deterioration.  In  temperate  climates  it  is  assumed  that 
the  temperature  of  the  surrounding  air  will  rise  to  90°  F.  or 
34°  C.  and  on  this  basis  the  increase  in  temperature  above 
that  of  the  surrounding  air  has  been  fixed  at  40°  C.  To  obtain 
a  smaller  rise  would  increase  the  cost  of  the  dynamo  or  motor  by 
an  amount  in  excess  of  the  value  which  would  accrue,  while  if 
the  machine  were  made  at  a  less  cost  for  a  greater  temperature  rise 
the  insulation  would  deteriorate  too  rapidly  and  the  efficiency  be  too 
much  reduced  to  make  such  machines  desirable  at  any  price.  The 
standard  fixed,  of  between  35  and  40°  C.,  is  a  commercial  com- 
promise between  ideal  scientific,  and  practical  business  conditions. 
Dynamos  which  are  to  be  installed  in  places  where  the  tempera- 
ture of  the  surrounding  air  will  be  greater  than  90°  F.  or  34° 
C.,  such  as  in  tropical  latitudes  or  adjacent  to  boiler  plants, 
must  have  a  corresponding  allowance  made  in  the  permissible 
temperature  rise.  Thus,  if  the  dynamo-room  is  subject  to  a  tem- 
perature of  44°  C.  for  a  prolonged  period  of  time,  the  allowable 


ALTERNATING- CURRENT  DYNAMOS  89 

temperature  rise  of  the  dynamos  should  be  limited  to  30°  C.  If 
this  high  temperature  is  attained  only  occasionally,  the  tempera- 
ture rise  and  total  temperature  attained  may  be  5  or  10°  C.  in 
excess  of  these  figures. 

From  these  considerations  it  is  obvious  that  dynamo-rooms 
should  be  as  well  ventilated  and  maintained  as  cool  as  possible. 

Exciting  Dynamos.     The  small  direct-current  dvnamos  which 


FIG.  45. 

supply  current  to  energize  or  "  excite"  the  field  magnets  of  the  gen- 
erators are  usually  standard  125  or  250  volt  machines.  In  small 
power  stations  it  is  usual  to  drive  the  exciter  by  means  of  a  belt 
which  receives  its  power  from  a  pulley  on  the  shaft  of  the  main 
dynamo.  Fig.  45  shows  this  arrangement.  In  some  instances  the 
exciter  is  mounted  on  the  same  frame  with  the  main  dynamo  and  its 
armature  is  placed  on  an  extension  of  the  main  dynamo  shaft,  pro- 
ducing in  effect,  an  exciter  direct-connected  to  the  main  dynamo. 
This  is  shown  in  Fig.  46.  It  has  the  advantage  of  eliminating 


9° 


DEVELOPMENT   AND    DISTRIBUTION   OF   WATER   POWER 


the  driving  belt  and  pulley  and  requiring  less  space  for  each  unit. 
It,  however,  has  the  disadvantage  that  the  small  machine  runs  at 
the  same  speed  as  the  large  one  to  which  it  is  connected  and  this, 
of  course,  is  necessarily  an  extremely  low  speed  for  the  small  ma- 
chine. As  a  result  the  cost  of  the  exciter  becomes  abnormally 
great  and  its  efficiency  also  is  reduced. 

With  either  the  belted  or  direct-connected  exciter,  each  alter- 


FIG.  46. 

nator  is  provided  with  its  individual  exciter.  In  the  larger  power 
stations  it  is  customary  to  install  only  two  exciters  regardless 
of  the  number  of  alternating-current  generators.  Each  of  these 
machines  is  driven  by  its  own  turbine  to  which  it  usually  is  direct- 
connected  except  when  the  head  on  the  water-wheels  is  too  low  to 
obtain  a  turbine  speed  corresponding  to  the  excrter  speed.  The 
sizes  of  the  exciters  and  their  driving  turbines  are  such  that  either 
exciter  will  furnish  sufficient  current  to  energize  the  field  magnets 


ALTERNATING-CURRENT    DYNAMOS  91 

of  all  the  generators  in  the  station.     Only  one  exciter  is  operated, 
the  other  being  held  in  reserve  as  a  spare  in  case  of  accident. 

Fig.  47  shows  the  usual  connections  between  the  exciters  and 
generator  fields.  Ei  and  £2  are  exciter  armatures  connected  to 
the  bus-bars  Z,i,  L2,  by  switches  Si,  52  respectively,  -n,  ;-2  are 
rheostats  in  the  exciter  fields  to  adjust  their  voltages.  Fi  and  F2 
are  the  generator  fields  connected  to  the  bus-bars  by  the  field 
switches  FSi  and  FS2.  Rheostats  Ri  and  R2  arc  inserted  in  the 
generator-field  circuits  so  that  the  excitation  of  these  fields  may  be 
adjusted  independently  of  each  other.  When  each  generator  is  pro- 


FIG.  47. 

vided  with  its  own  separate  exciter,  the  excitation  of  the  generator 
field  is  varied  by  adjusting  the  exciter-field  rheostat  so  that  the  exciter 
armature  gives  just  the  required  voltage  to  produce  the  desired  field 
excitation,  the  resistance  of  the  main  dynamo  rheostat  being  prac- 
tically all  cut  out,  thus  minimizing  the  energy  loss  from  the  exciter. 

As  explained  in  discussing  temperature  rise  of  the  main  dyna- 
mos, the  capacity  of  exciters  should  be  such  that  they  will  never 
attain  a  temperature  above  74°  C. 

The  exciting  current  required  by  any  alternating-current  genera- 
tor should  not  vary  greatly  with  change  in  load  on  the  generator. 
It  is  usual  to  specify  that  the  required  field  excitation  at  full  load 
with  80  per  cent,  power  factor  shall  not  be  more  than  20  per  cent, 
in  excess  of  that  required  to  produce  the  same  voltage  at  zero  load, 
the  speed  of  the  generator  being  the  same  under  both  conditions. 

The  proper  voltage  of  generators  is  fixed  by  the  transmission 
conditions  which  are  discussed  in  chapter  IX. 


CHAPTER  VIII. 
TRANSFORMERS. 

As  will  be  presently  set  forth  under  the  subject  "Transmission 
Lines,"  high  voltages  are  essential  on  long-distance  lines  for  com- 
mercial reasons.  Generally,  where  the  pressures  exceed  6,600 
volts  it  is  not  expedient  to  produce  it  directly  in  the  generator  wind- 
ings, and  transformers  are  used  which  receive  the  generator  cur- 
rent at  some  low  voltage  and  transform  it  into  practically  the  same 
amount  of  electrical  energy  of  less  current  at  much  greater  voltage. 
When  so  used  they  are  termed  "step-up"  transformers.  The 
generator  voltage  when  step-up  transformers  are  used  may  be 
anything  desired,  as  the  cost  of  transformers  is  dependent  only 
on  their  K.W.  capacity  and  the  voltage  of  the  high-tension  side. 
It  is  usual,  therefore,  to  install  generators  that  give  1,000  to  2,000 
volts,  where  step-up  transformers  are  used  to  produce  the  necessary 
line  pressure,  and  in  many  cases  440  volt  generators  are  adopted. 
It  is  better  to  use  low-voltage  dynamos  in  connection  with  step-up 
transformers,  as  they  are  less  dangerous,  there  is  less  liability  to 
break-down  due  to  failure  of  insulation,  and  the  switchboard  equip- 
ment is  reduced  in  cost,  except  in  cases  where  the  kilo-watt  capacity 
of  the  plant  is  so  great  that  the  currents  at  the  lower  voltage  be- 
come extremely  large,  in  which  event  the  excessive  size  of  the 
switches  and  instruments  and  the  panels  on  which  they  are  mount- 
ed makes  the  cost  of  the  switchboard  equipment  higher  than  it 
would  be  for  smaller  devices  constructed  to  work  under  greater 
pressures. 

The  high  tensions  used  for  transmission  are  not  suitable  nor  ap- 
plicable to  motors,  lamps,  or  other  translating  devices,  and  it  there- 
fore is  necessary  to  reduce  the  voltage  at  the  receiving  end  of  the 

92 


TRANSFORMERS 


93 


transmission  line,  which  reduction  is  effected  by  means  of  trans- 
formers similar  to  the  step-up  transformers.  Where  they  are  used 
for  voltage  reduction  they  are  called  "step-down"  transformers. 

The  transformers  at  the  power  station  are  usually  located  in 
an  extension  of  the  dynamo -room.  When  they  are  small,  say  not 
above  100  K.W.  in  size,  they  are  placed  in  rows  in  the  extension 
provided  for  them,  with  ample  space  around  each  one  so  that  it 
may  be  inspected  from  every  side.  In  the  case  of  large  transform- 
ers, the  best  practice  requires  that  a  separate  brick  or  concrete 
chamber  be  constructed  for  each  transformer,  with  a  door  of  iron 
on  the  front  of  each  chamber,  made  to  slide  or  to  roll  out  of  place 
so  that  the  clear  opening  obtained  when  the  door  is  moved  is  equal 
practically  to  the  area  of  one  side  of  the  chamber.  In  practice 
the  construction  adopted  is  to  make  a  long  room  of  comparatively 
small  height  and  depth  and  separated  into  a  number  of  compart- 
ments by  means  of  concrete  or  masonry  division  walls,  each  com- 
partment being  a  fire-proof  containing-chamber  into  which  a 
single  transformer  may  be  placed.  This  arrangement  is  particu- 
larly necessary  in  the  case  of  oil-cooled  transformers,  as  there  is 
danger  of  conflagration  at  times  when  sudden  arcs  occur  due  to 
break-down  of  insulation  which  sometimes  takes  place.  These 
fire-proof  chambers  add  but  little  to  the  cost  of  a  power-house  and 
should  always  be  installed  when  practicable.  They  give  the 
additional  advantage  of  preventing  the  attendants  from  coming 
in  contact  with  the  high-tension  terminals  or  receiving  dangerous 
shocks  from  static  discharges  which  sometimes  occur. 

In  order  to  render  the  transformers  accessible  for  inspection 
and  repair,  they  are  usually  mounted  on  an  iron  frame  having  small 
rollers  under  them,  so  that  any  one  may  be  rolled  out  of  its  com- 
partment with  ease  and  quickness.  Many  stations  have  the  floor 
level  of  the  transformer  chambers  about  twenty  inches  above  the 
floor  level  of  the  station  itself,  with  a  track  running  along  in  front 
of  the  row  of  compartments.  A  small  car,  having  its  platform  on  a 
level  with  the  floor  of  the  compartments,  runs  on  this  track,  and 
with  this  arrangement  any  transformer  may  be  rolled  out  onto  the 


94          DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

car  and  conveyed  to  the  repair-room  or  any  other  place  provided 
for  inspection  and  repair  of  these  devices.  This  is  a  somewhat 
elaborate  construction  and  suitable  only  for  the  larger  power- 
houses of  6,000  K.W.  or  more. 

Some  engineers  prefer  to  construct  a  separate  building  for  the 
transformers,  a  short  distance  from  the  generating  station.  This 
is  by  no  means  a  necessary  plan,  however,  and  its  general  adoption 
is  not  to  be  advised,  though  certain  peculiar  conditions  may  some- 
times make  it  desirable. 

Transformers  being  simply  special  forms  of  electric  generators 
in  which  the  lines  of  forces  are  cut  by  varying  the  magnetic  flux 
instead  of  mechanical  rotation,  they  are  subject  to  the  same  laws 
and  commercial  considerations  as  are  the  dynamos  in  the  power 
plant.  They  are  subject  to  temperature  rise,  and  in  order  to  cut 
down  their  cost  for  a  given  output  it  is  customary  to  employ  some 
means  of  artificially  cooling  them,  when  they  reach  a  size  of  100 
K.W.  or  more. 

The  methods  of  cooling  in  general  use  are:  (i)  by  an  air  blast 
from  a  blower;  (2)  by  filling  the  transformer  case  with  oil  which 
is  circulated  through  pipes  that  are  surrounded  by  water  which  ab- 
stracts the  heat  from  the  oil,  thus  maintaining  the  temperature  in 
the  case  at  a  safely  moderate  value",  and  (3)  by  arranging  a  coil 
of  pipe  inside  the  transformer  case,  the  case  being  filled  with  oil, 
and  circulating  water  through  the  pipe  coil  and  thereby  abstracting 
the  heat  from  the  oil.  Fig.  48  shows  the  last-named  type  with 
the  casing  removed.  The  coil  of  pipe  for  the  circulation  of  cooling 
water  is  clearly  shown. 

The  air-blast  transformers  are  generally  used  in  the  sub-stations 
at  the  end  of  the  line,  while  the  oil-filled  transformers,  cooled  by  a 
coil  of  water-filled  pipe  inside  the  casing,  are  used  at  the  power 
station  for  raising  the  transmission  voltage,  it  being  usually  the  case 
that  plenty  of  water  for  cooling  purposes  is  available  at  the  power 
station,  while  little  or  none  is  obtainable  at  the  sub-station  unless 
purchased  from  a  water-supply  company  at  prohibitive  rates. 

At  the  power  station,  the  cost  of  maintaining  the  water  cir- 


TRANSFORMERS 


95 


dilation  is  nil,  as  the  head  on  the  water-wheels  will  also  force  water 
through  the  cooling  coils.  When  the  transformers  are  placed 
above  the  level  of  the  head  water,  a  siphon  arrangement  can  be 


FIG.  48. 

used  if  the  maximum  lift  of  the  water  is  not  over  ten  feet  above  the 
level  of  the  head  water  and  the  head  itself  is  twenty  feet  or  more. 

The  oil  in  the  transformer  case  acts  also  as  an  insulator  pre- 
venting break-downs  and  re-insulating  any  puncture  that  may 
occur  due  to  abnormal  voltages  from  surges  on  the  line.  It  also 
prolongs  the  life  of  the  insulating  materials  used  in  the  construc- 
tion of  the  coils,  so  that  its  value  is  twofold. 


g6          DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

As  in  the  case  of  generators,  transformers  have  a  certain  effi- 
ciency and  regulation  and  these  are  dependent  on  the  amounts  of 
copper  and  iron  used  in  their  construction  and,  therefore,  on  the  cost. 

Good  transformers  have  efficiencies  ranging  from  96  to  98 
per  cent.,  depending  on  the  size  and  design.  The  regulation  is 
from  3  to  7  per  cent.  The  desirable  efficiency  is  a  commercial 
question  and  determined  in  the  same  manner  that  the  efficiency 
of  the  generators  is  fixed.  The  regulation  is  also  settled  by  the 
same  considerations  which  govern  the  selection  of  the  generator 
regulation. 

This  latter,  however,  is  not  a  serious  matter  if  automatic  volt- 
age regulators  be  used. 

The  capacity  of  the  transformers  is  determined  by  the  method 
of  computation  given  in  chapter  IX.  In  three-phase  systems  any 
number  of  generators  may  be  used,  all  working  in  parallel  and  all 
delivering  their  power  to  one  set  of  bus-bars.  From  these  bus- 
bars, the  power  passes  to  the  transformers  which  are  also  con- 
nected in  parallel  to  a  set  of  high-tension  bus-bars  which  latter 
supply  current  to  the  transmission  line.  With  this  arrangement, 
it  is  evident  that  the  number  of  transformers  necessary  bears  no  re- 
lation to  the  number  of  generators.  For  3-phase  systems  the 
number  of  transformers  must  be  divisible  by  three,  however,  as 
there  are  three  high-tension  bus-bars  to  deliver  current  to  three 
outgoing  transmission  wires. 

Many  engineers  prefer  to  install  three  transformers  for  each 
generator,  with  switching  arrangements  for  connecting  any  three 
transformers  to  any  one  of  the  generators  direct,  and  putting  the 
high- voltage  windings  of  the  transformers,  only,  in  parallel.  There 
is  no  good  reason  for  this  practice  and  there  are  several  reasons 
against  it.  A  given  capacity  costs  less  in  a  few  large-size  trans- 
formers than  it  does  in  a  larger  number  of  smaller  sizes  and,  also, 
each  transformer  is  a  possible  source  of  trouble  and  it  is  not  good 
practice  to  multiply  any  such  possibilities.  Large  transformers 
have  a  slightly  higher  efficiency  for  the  same  character  or  con- 
struction than  smaller  ones. 


TRANSFORMERS 


97 


Transformers  should  be  well  protected  against  lightning,  as 
they  receive  any  discharge  that  reaches  the  station.  They  should 
always  have  their  cases  well  grounded,  so  that  there  can  never  be 
any  dangerous  potential  between  the  case  and  the  earth  to  imperil 
the  lives  of  the  attendants.  Recent  practice  seems  to  favor  con- 
necting the  secondary  windings  to  earth,  so  that  in  case  of  a  break- 
down of  the  insulation  between  the  high-tension  and  low-tension 
windings,  no  high  voltage  can  be  maintained  between  the  low- 
tension  winding  and  the  earth. 

There  are  three  general  methods  of  connecting  transformers 
for  three-phase  circuits;  namely,  Y  connection,  A  or  mesh  con- 
nection, and  resultant  mesh  connection.  The  first  two  methods  re- 
quire three  transformers  or  a  number  which  are  connected  in  three 
parallel  groups,  wrhile  the  third  method  requires  only  two  transform- 
ers or  a  number  which  are  connected  to  form  two  parallel  groups. 

The  Y  connection  is  shown  in  Fig.  49.  Pl  P2  P3  represent 
the  primary  windings  of  trans- 
formers i,  2  and  3,  respectively, 
Ti  T-2  T3,  the  three  wires  of  the 
incoming  transmission  line,  Si  S2 
S3  the  secondary  windings  of  the 
three  transformers,  and  Dl  D2  D3 
the  wires  of  the  distribution  cir- 
cuit. As  is  clear  from  the  figure, 
a  high-tension  wire  is  connected 
to  one  side  of  each  primary  wind- 
ing of  each  transformer,  the  other 
three  terminals  of  the  windings 

being  joined  together.  Similarly,  the  three  secondary  windings 
have  each  a  terminal  connected  to  one  of  the  distribution  wires, 
while  the  other  three  terminals  are  joined  together. 

The  A  or  mesh  connection  is  as  shown  in  Fig.  50.  One  ter- 
minal of  the  primary  Pl  is  joined  to  a  terminal  of  P2,  the  other  side 
of  P2  being  connected  to  a  terminal  of  P3,  while  the  remaining  ter- 
minals of  Pi  and  P3  are  joined  together.  The  three  transmission 


TI. 

T2 

I/W!AAA) 

A/Wwv         l/vwvvA/v 

FIG.  49- 


98 


DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 


wires  7^  T2  and  T3  connect  to  the  three  junctions  between  the  coils 
as  indicated.     The  connections  of  the  secondary  coils  to  the  three 


FIG.  50. 

distributing  wires  are  made  in  a  similar  manner  and  are  obvious 
from  the  figure. 

The  resultant  mesh  connection,  made  with  two  transformers 
is  depicted  in  Fig.  51.  The  two  primary  coils  of  the  two  trans- 
formers are  connected  together  on  one  side  as  shown,  while  the 
other  two  sides  are  connected  to  the  transmission  wires  7^  and  T3. 

T2  is  connected  to  the  common 
junction  point  between  the  two 
primary  coils  P1  and  P2.  The 
connections  on  the  low-tension 
or  distribution  side  are  exactly 
similar  and  easily  followed  from 
the  diagram. 

Each  of  these  methods  of 
connecting  transformers  has  cer- 
tain advantages,  and  the  selection 
between  the  Y  and  the  A  seems 
to  be  largely  a  matter  of  personal 
preference  rather  than  any  real  superiority.  The  resultant  mesh 


vwiw\_  _/www\ 


Si 


D,., 


D, 


FIG.  51. 


TRANSFORMERS  99 

is  not  suitable  for  large  powers  and  has  its  field  of  usefulness 
limited  to  supplying  current  to  small  motors,  acting  as  a  step-down 
transforming  system. 

In  general,  transformers  for  a  given  capacity  and  voltage  are 
slightly  cheaper  and  smaller  when  connected  in  Y  fashion  than 
when  connected  in  mesh.  On  the  other  hand,  the  mesh  connec- 
tion has  the  advantage  that  if  one  of  three  transformers  should 
break  down  it  may  be  cut  out  and  the  operation  of  the  plant  would 
not  be  interrupted,  the  remaining  two  transformers  working  as 
resultant  mesh-connected  units.  The  two  can,  of  course,  deliver 
only  about  sixty-six  per  cent,  of  the  required  energy  if  they  work  at 
their  normal  rating,  but  by  overloading  them  fifty  per  cent,  and  at 
the  same  time  increasing  to  the  highest  possible  amount  the  cir- 
culation of  the  cooling  medium — whether  air  or  water — the  full 
load  may  probably  be  carried  for  one  or  two  hours  without  injury 
to  the  overloaded  transformers.  For  this  reason  the  majority  of 
plants  have  adopted  the  mesh  connection. 

A  spare  transformer  should  be  kept  in  every  power  station 
ready  to  connect  quickly  in  case  of  accident  to  any  one  of  the 
operating  transformers,  and  where  they  are  all  mounted  on  rollers, 
the  removal  of  an  injured  transformer  and  the  substitution  of  a 
spare  one  is  accomplished  expeditiously. 


CHAPTER  IX. 

TRANSMISSION  CONDUCTORS. 

TRANSMISSION  lines  from  the  power  station  to  the  point  of  dis- 
tribution, or  to  the  town  limits  of  a  city,  are  always  of  bare  un- 
insulated wire.  Copper  is  generally  employed,  though  aluminum 
is  occasionally  used. 

The  electrical  problems  which  are  involved  comprise :  (i)  the 
determination  of  the  sizes  of  wires  and  their  relative  positions  to 
carry  a  given  amount  of  energy  over  the  distance  from  power 
station  to  point  of  distribution  with  a  specified  loss  in  energy; 
(2)  the  calculation  of  the  necessary  voltage  at  the  power  station  to 
produce  the  required  voltage  at  the  receiving  end  of  the  line;  (3) 
the  computation  of  the  energy  required  at  the  dynamo  to  deliver 
the  given  energy  at  the  receiving  end  of  the  line ;  (4)  the  calculation 
of  the  sizes  of  dynamos  and  transformers  necessary  to  deliver  the 
specified  energy;  and  (5)  the  protection  of  the  line  against  lightning 
discharges.  The  mechanical  problems  are:  (i)  the  method  of 
supporting  the  wires  on  insulators;  (2)  the  strains  in  wires,  poles, 
pins,  cross  arms,  and  insulators  which  are  allowable ;  (3)  the  proper 
organization  of  the  pole  line. 

Taking  up  first  the  electrical  problems,  the  examples  given  later 
show  the  methods  employed  to  compute  the  first  four  mentioned. 

Standard  wires. — Wires  are  given  arbitrary  gauge  numbers,  a 
certain  diameter  and  area  corresponding  to  a  given  gauge  num- 
ber. In  electrical  computations  the  circular  mil  is  the  unit  gener- 
ally used.  The  number  of  circular  mils  (abbreviation,  cir.  mil) 
in  a  wire  is  equal  to  1,000  times  the  diameter  in  inches  squared. 
Thus  a  wire  0.25  inch  in  diameter  has  an  area  of  (0.25  X  iooo)2 
=  62,500  circular  mils.  The  actual  area  of  a  wire,  in  square  in- 
ches, is  equal  to  cir.  mils  X  0.7854  -5-  1,000,000.  The  following 

IOO 


TRANSMISSION   CONDUCTORS 


101 


wire  table  gives  the  gauge  numbers  of  various  sizes  of  copper 
wire,  the  diameter  in  inches,  the  number  of  cir.  mils  in  each,  the 
resistance  in  ohms  per  1,000  feet,  and  the  weight  in  pounds  per 
i, ooo  feet  and  per  mile  of  soft-drawn  copper: 

BARE  COPPER  WIRE. 
Dimensions  and  Weights. 


B.  &  S. 
gauge. 

Circular 
mils. 

Diameter, 
mils. 

Pounds 
per  1,000  ft. 

Pounds 
per  mile. 

0000 
000 

oo 
o 

211,600.00 
167,802.93 

I33>079-04 
105,534.02 

460.000 
409  .  640 
364  .  800 
324.860 

639-33 
507.01 
402.09 
318.86 

3,375-66 
2,677.01 
2,123.03 
1,683.58 

I 

2 

3 
4 

83,694.49 
66,373.22 

52,633.54 
41,742.58 

289.300 
257.630 
229.420 
204.310 

252.88 
200.54 
159-03 

126.  12 

1.335  -2i 

1,058.85 
839.68 
665.91 

1 

33,102.16 
26,250.48 
20,816.72 

181.940 
162.020 
144.280 

100.  OI 

79-32 
62.90 

528-°5 
418.81 

332." 

BARE  COPPER  WIRE. 
Resistance  Calculated  at  70°  F. 


Ohms   per 

I,  OOO  It. 

Ohms  per 

1,000  ft. 

Ohms  per 
mile. 

Feet  per 
ohm. 

Ohms  per 
pound. 

oooo 
ooo 
oo 

0 

0.04893 
0.06170 
0.07780 
0.09811 

0.2621 
0.3306 
0.4168 

0-5251 

20,147 
15,972 
12,668 
10,055 

0.0000776 
0.0001234 
0.0001962 
0.0003114 

I 

2 

3 
4 

°-I233 
o.  1560 
0.1967 
0.2500 

0.6627 
0.8360 
1.054 
1.329 

7,968 
6,316 
5,010 
3.974 

o  .  0004960 
0.0007894 
0.001254 
0.001994 

5 
6 

7 

0.3124 
0.4000 
0.5044 

1.676 
2.113 
2.663 

3,i5o 
2,499 
1,982 

0.003173 
0.005043 
0.008013 

Hard-drawn  copper  wire  is  frequently  used  where  the  spans 
are  particularly  long,  because  of  its  greater  tensile  strength.     The 


« 


102       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

strength  of  soft-drawn  copper  is  about  30,000  Ibs.  per  square  inch, 
while  hard-drawn  copper  has  a  strength  of  double  this,  or  60,000 
Ibs.  per  square  inch.  The  resistance  of  hard  -drawn  copper  is 
about  5  per  cent,  greater  than  that  of  soft-drawn,  and  this  percentage 
should  be  added  to  the  tabular  resistances  as  given,  when  hard- 
drawn  copper  is  to  be  used. 

To  compute  the  size  of  wire  for  a  direct-current  transmission 
line,  the  allowable  loss  in  the  line  must  be  assumed.  The  current 
in  the  line  will  be  equal  to  the  kilo-watts  X  1,000  divided  by  the 

voltage,    or  I  =  —  —  .     The  size  of  wire  required  is  equal 

E 

2  X  D  X  I  X  ii  . 

to  —  m  circular  mils.  I  is  the  current,  in  amperes, 

E  X  p 

D  is  the  distance  of  transmission  in  feet,  E  is  the  voltage  at  the  re- 
ceiving end  of  the  line,  p  is  the  loss  allowed.  The  energy  loss  in 
a  circuit  is  equal  always  to  the  resistance  X  (current)2,  x)r,  loss  = 
PR.  As  an  example,  assume  a  2  -mile  transmission'  (  =  2  X  5,280 
=  10,560  feet),  250  K.W.  to  be  delivered,  the  voltage  at  the  receiv- 
ing end  to  be  520  volts  and  the  loss  to  be  10  per  cent.  Current  = 

2^0  X  1000  2  X  10,560  X  482  X  ii 

=  482  amp.     cir.  mils.  =  —  —  =  2,- 


520  520  X  o.io 

150,000  cir.  mils. 

This  nearly  corresponds  to  10  wires  No.  oooo  size  as  given 
in  the  table.  The  total  weight  per  1,000  feet  is  640.5  X  10=  6,405 
Ibs.  The  total  length  of  wire  is  twice  the  distance  of  transmission  = 
2  X  10,560  =  2  1,  1  20  ft.  Total  weight  of  wire  =  21,120  X  6,405  -^ 
1,000  =  135,000  Ibs.  Add  3  percent,  for  sag  and  joints  =13  5,000  + 
4,050  =  139,050  Ibs.  The  resistance  of  the  circuit  is  one-tenth  the 
resistance  of  a  single  circuit  of  No.  oooo,  there  being  ten  wires  in 
parallel.  The  resistance  of  a  No.  oooo  wire  is  about  0.05  ohm 
per  1,000  ft.,  and  the  resistance  of  a  complete  circuit  of  this 
size  wire  is,  for  this  distance  of  transmission,  21,120  X  0.05  = 
1.056  ohms.  Resistance  of  10  wires  in  parallel  =  1.056.  -*•  10 
=  0.1056  ohm. 


TRANSMISSION   CONDUCTORS 


,  I03 


Voltage  drop  in  the  line  =  amperes  X  ohms  =  482  X  0.1056  = 
51  volts. 

Voltage  at  the  generator  =  volts  at  receiving  end  +  volts  drop  = 
520  +  51  =  571  volts.  Actual  loss  =  P  X  R=  (482 )2  X  0.105  = 

24.5 

24,500  watts  =  24.  5  K.W.     Per  cent.  less=         =9.82  per  cent. 

250 

If  the  K.W.  capacity,  the  transmission  distance,  and  the  per- 
centage loss  be  the  same  as  before,  but  the  voltage  at  the  receiving 
end  is  1,040  volts,  or  double  the  previously  assumed  value,  the 
amount  of  copper  required  will  be  greatly  reduced. 

250  X  1,000 

Current  =  =240.5  amps. 

1,040 

2   X   10.560  X   240.5.   X   ii 

Cir.  mils.  =  -  =  537.500. 

1,040  X  o.io 

Compared  with  the  cir.  mils  required  for  the  previous  case  it  is 
seen  that  this  is  just  one-fourth  the  amount  computed  for  a  520- 
volt  pressure.  As  a  matter  of  fact,  the  amount  of  copper  re- 
quired is  inversely  as  the  square  of  the  voltage  oj  transmission. 
This  is  the  reason  for  the  employment  of  high  voltages  on  long 
transmission  lines. 

In  very  short  lines  the  size  of  wire  may  be  fixed,  not  by  the  drop 
in  the  line,  but  by  the  current-carry- 
ing capacity  of  the  wire.  A  given 
size  of  wire  can  carry  only  a  certain 
current,  regardless  of  the  drop  or  loss. 
The  adjoining  table  gives  the  maxi- 
mum currents  allowable  in  various- 
size  bare  wires,  to  Brown  and  Sharpe 
gauge. 

In  alternating- current  transmission 
lines  there  is  an  inductive  drop  as  well 
as   the   drop   due   to  the  resistance. 
This  makes  the  total  line  drop  greater  than  in  the  case  of  direct  or 
continuous  currents.     The  energy  loss,  however,  is  only  that  due 


Size  of 
wire. 

Allowable 
current. 

0000 

400  amps. 

000 

320 

00 

270 

o 

240 

I 

190 

2 

160 

3 

135 

4 

"5 

5 

92 

6 

80 

104       DEVELOPMENT   AND   DISTRIBUTION  OF   WATER   POWER 

to  the  product  of  the  square  of  the  current  flow  and  the  resistance 
of  the  line,  and  is  not  equal  to  the  drop  multiplied  by  the  current. 

Take  as  an  example  a  single-phase  transmission  of  750  K.W. 
to  be  delivered  at  the  receiving  end;  voltage  10,000  volts;  dis- 
tance 14  miles;  energy  loss  10  per  cent.;  power  factor  0.85;  fre- 
quency 25  cycles  per  second;  wires  of  circuit  36  inches  apart; 
step-up  and  step-down  transformers  used  having  efficiencies  of 
97  per  cent. 

The  apparent  kilo- watts  or  K.V.A.,  delivered  at  the  receiving 

end  will  be  the  actual  K.W.  divided  by  the  power  factor  = = 

0.85 

882.3  K.V.A. 

Actual  energy  delivered  to  the  step-down  transformers  = 

0.97 

=  773  K.W. 

Apparent  K.W.  delivered  to  step-down  transformers  =  -^  = 

0.85 

910  K.V.A.,  which  is  the  apparent  energy  transmitted  over  the 
line. 

910  X   1,000 

Current  in  the  circuit  =  —  —  =91  amps.     Loss  is  to 

10,000 

be  10  per  cent,  of  the  delivered  energy  =  75  K.W.  =  75,000  watts. 

Loss  in  watts  also  equals  I2xR=(9i)2  XR. 

(9i)2XR  =  75    K.W.,    R  =  75 X  1,000  =          ^^ 

(91) 

The  resistance  per  1,000  feet  is  equal  to  the  total  resistance  as 
found  above,  divided  by  the  number  of  thousands  of  feet  in  the 
complete  circuit,  which  is  equal  to  twice  the  transmission  dis- 
tance, there  being  two  wires  to  each  circuit. 

9.07  9-°7 

Res.  per  1,000  feet  =—  --=-1,000  = =0.0613 

2   X  14  X  5,280  148 

ohm. 

From  the  table,  this  corresponds  most  nearly  to  No.  ooo  wire, 
which  should  be  adopted.  The  actual  resistance  of  No.  ooo 


TRANSMISSION   CONDUCTORS 


105 


is  0.0617  per  1,000  feet,  which  makes  the  resistance  of  the  circuit  = 
148  )(  0.0617  =  9.14  ohms,  148  being  the  length  of  the  circuit  in 
thousands  of  feet.  The  volts  drop  due  to  resistance  will  be  equal 
to  the  current  X  the  resistance  =  91  X  9.14  =  831  volts. 

To  find  the  volts  drop  due  to  reactance  consult  the  table  fol- 
lowing : 

DISTANCE  APART  OF  CONDUCTORS.* 


Size  of 
Wire 

Twelve 
inches 

Eighteen 
inches 

Twenty-four 
inches 

Thirty 
inches 

Thirty-  six 
inches 

0000 

.IQ3                            .212 

.225 

-235 

.244 

000 

.199 

.217 

.230 

.241 

-249 

00 

.204 

.222 

.236 

.246 

.254 

0 

.209 

.228 

.241 

•251 

-259 

I 

-214 

-233 

.246 

.256 

.265 

2 

.220 

.238 

.252 

.262 

.270 

3 

.225 

.244 

-257 

.267 

•275 

4 

.230 

.249 

.262 

.272 

.281 

5 

.236              .254 

.268 

.278 

.286 

6 

.241                   .260 

.272 

.283 

.291 

*  Reactance  volts  in  1,000  feet  of  line  ( =  2,000  feet  of  wire)  for  one  ampere  att7,2oo  alter- 
nations per  minute  (60  cycles  per  second)  for  the  distance  given  between  centres  of 
conductors. 

The  values  given  in  this  table  are  for  frequencies  of  60  cycles  per 
second.  To  find  the  factor  for  other  frequencies,  multiply  the 
factor  in  the  table  by  the  frequency,  and  divide  the  product  by  60. 
The  result  will  be  the  reactance  factor  for  the  desired  frequency. 

From  the  table  the  reactance  volts  per  1,000  feet  of  transmission 
distance  (  =  2,000  feet  of  circuit)  for  No.  ooo  wires  placed  36  inches 
apart  is  0.249  vo^  for  each  ampere  flowing  when  the  frequency 
is  60  cycles  per  second.  Therefore,  the  reactance  volts  for  the  case 
under  consideration  and  basis  of  60  cycles  would  be  (14  X  5,280  -*• 
i ,000)  X  91  X  0.249  =  74  X  91  X  0.249  =  1,678  volts.  The  factor 
0.249  is>  however,  for  a  frequency  of  60  cycles,  and  the  frequency 
of  the  system  under  discussion  is  25  cycles.  Therefore  the  above 
value  must  be  changed  to  one  proportional  to  the  frequency,  and 

the  actual  volts  will  be,  — —  =  700  volts. 

60 


106       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

The  line  drop  is  equal  to  the  square  root  of  the  sum  of  the 
resistance  drop  squared  and  the  reactance  volts  squared,  or  drop  = 
V(res.  volts)2  +  (react,  volts)2  =  ^(831)'  +  (7oo)2  =  i ,086  volts. 

The  energy  loss  =  I2  R=(9i)2  X  9.14  =  75.8  K.W.  =  io.i  per 
cent,  of  the  delivered  power. 

Apparent  energy  loss  in  line  =  volts  drop  X  line  current  =  i, 086 
X  91  =98.8  K.V.A. 

Actual  energy  to  be  delivered  by  the  step-up  transformers  is 
that  delivered  to  the  step-down  transformers  +  loss  in  the  line  = 
773  K.W.  +  75.8  K.W.  =  848.8  K.W. 

The  apparent  energy  delivered  by  the  step-up  transformers 
is  equal  to  the  apparent  energy  delivered  to  the  step-down  trans- 
formers +  apparent  energy  lost  in  the  line  =  910  -f-  98.8  =  1,008.8 
K.V.A. 

Actual  energy  delivered  to  the  step-up  transformers  is  equal 
to  their  output  divided  by  their  efficiency — 97  per  cent,  in  this  case: 

0.0    O 

Energy  —  _ 1  =875  K.W.,  which  is  the  actual  energy  the  dynamo 
0.97 

must  deliver  to  the  step-up  transformers. 

The  apparent  energy  delivered  to  the  step-up  transformers  is 
equal  to  the  apparent  energy  delivered  by  them  to  the  line,  divi- 
ded by  the  transformer  efficiency  =  — —  =  1,040  K.V.A.,  which 

0.97 

is  the  required  dynamo  capacity. 

The  computations,  then,  summarized,  are  as  follows: 

Size  of  generating  equipment 1,040  K.  V.  A. 

Size  of  step-up   transformers 1,008.8  K.  V.  A. 

Size  of  step-down  transformers. 910  K.  V.  A. 

Size  of  line  wire,  No.  ooo  B.  &  S.  gauge. 

Total  losses   in    system    from    generator  to  motors  = 

875—75° I25  K.  W. 

Current  in  line 91  amps. 

Voltage  of  step-up  transformer  =10,000  +  1,086  =  11,086  volts. 
The  power  required  at  the  turbine  shaft,  if  the  dynamo  em- 


TRANSMISSION  CONDUCTORS  107 

ciency  is  94  per  cent,  will  be  equal  to  the  actual  energy  deliv- 
ered by  the  dynamo  divided  by  its  efficiency.     This  is  equal  to 

—  =^31  K.W.=  1,246  H.P. 
0.94 

The  size  of  the  turbine  should  be  increased  by  about  20  per 
cent,  to  take  care  of  speed  regulation  and  wear.  This  would  make 
the  turbine  power  1,506  H.P.  If  the  efficiency  of  the  turbine  is 
80  per  cent.,  the  gross  hydraulic  power  necessary  to  deliver  the  750 

1,246 

K.W.  at  the  motors  is  -          =  1,557  H.P. 
.80 

The  plant  would  be  divided  into  three  units.  Each  turbine 
would  have  a  capacity  of  500  H.P.,  making  the  aggregate  1,500 
H.P.  Each  dynamo  would  give  350  K.V.A.,  making  1,050  K.V.A. 
total.  There  would  be  four  transformers  at  the  power  station  of 
250  K.V.A.  each,  giving  a  station-transformer  capacity  of  1,000 
K.V.A.  The  receiving  transformers  would  be  three  in  number, 
each  of  300  K.V.A.  capacity,  making  a  total  of  900  K.V.A.,  all  of 
which  figures  correspond  very  closely  to  the  actual  computed  re- 
quirements and  which  are  obtained  with  standard  apparatus. 

The  usual  transmission  is  three-phase,  a  circuit  being  made 
up  of  three  wires  of  equal  size  and  resistance.  There  are  two 
methods  of  computation  which  may  be  followed.  One  is  to  divide 
the  delivered  energy  by  2,  and  assume  a  single-phase  system 
supplying  this  half  the  total  energy.  On  this  basis,  compute  the 
size  of  wire,  the  resistance  drop,  the  reactance  drop,  and  total  drop 
as  given  in  preceding  example.  Each  of  the  three  wires  of  the 
three-phase  circuit  will  then  be  the  same  size  as  that  computed,  and 
the  drop  will  be  the  same.  The  more  complete  method,  is,  how- 
ever, fully  indicated  in  the  following  example: 

Assume  a  three-phase  system  to  deliver  8,000  K.W.  to  a 
distribution  circuit  fed  from  a  high-tension  transmission  line. 
Power  factor  of  the  distribution  circuit  =  0.88;  voltage  of  trans- 
mission at  receiving  end  =  2 5,000  volts;  distance  35  miles  (  = 
184,500  feet);  frequency  25  cycles;  energy  loss  in  transmission 
line  8  per  cent,  of  delivered  power;  dynamo  efficiency  95  per  cent.; 


IO8       DEVELOPMENT  AND   DISTRIBUTION   OF   WATER   POWER 

transformer  efficiency  97  per  cent.;  wires  24  inches  apart,  ar- 
ranged in  triangular  relationship  (see  Fig.  52). 

Actual  energy  delivered  by  step-down  transformer  =  8,000  K.W. 

Apparent  energy  =  actual  -j-  power  factor  =  —    —  =  9O9iK.V.A. 

0.88 

Energy  input  to  step-down  transformers  =  —    —  =  8,247  K.W. 

0.97 

actual. 

Apparent  energy  input  =- =— - — =9,361  K.V.A. 

power  factor      0.88 

Energy  loss  in  line  =  8  per  cent,  of  8,000  K.W.  =  640  K.W. 
The  actual  energy  transmitted  over  the  line  per  wire  is  one-third 

of  the  total  =  — 7  =  2,749  K.W. 
3 

The  apparent  energy  transmitted  over  the  line  per  wire  is  - 

=  3,120  K.V.A. 

In  any  three-phase  system  the  effective  voltage  is  equal  to  the 

line  voltage  divided  by  A/3  or  1.732. 

The    effective    voltage,   therefore,    of    this  system    is   — — 

1-732 

=  14,400  volts.  The  line  current  per  wire  =  apparent  energy 
per  wire  delivered  to  the  step-down  transformers  divided  by  the 

3,120  X  1,000 

effective  volts,  .which  for  this  case  =  —  —  =  217  amperes. 

14,400 

640 
I2  R=line  loss  =  640  K.W.  total  and  per  phase  =-  -  =213.3 

K.W. 

213.3   X   1,000         213.3   X   1,000 
R  =  — — —  =   -  —  =  4-S4  ohms. 

I2  (2I7)2 

This  is  the  total  resistance  of  one  wire,  which  in  computing  three- 
phase  lines  is  the  length  always  taken  instead  of  double  the 
length  of  transmission.  This  assumption  of  the  single  distance  is 


TRANSMISSION   CONDUCTORS  IOQ 

compensated  for  by  reducing  the  line  voltage  in  the  calculations 
in  the  ratio  of  i  to  1.732. 

Length  of  the  single  wire  =  184,500  feet. 

4.54 

Resistance  of  wire  per  1,000  ft.  =—        =0.0246  ohm. 

184.5 

This  resistance  is  less  than  that  of  a  No.  oooo  wire,  and  con- 
sequently should  be  divided  into  two  separate  circuits  at  least. 
The  current  per  wire  will  thus  be  halved,  and  the  resistance  per 
wire  correspondingly  increased. 

For  two  circuits: 

217 

I  =  —  =108.5   amperes  per  wire. 
2 

p  R=J'I3'3KA  '  =  106.6  K.W.  per  wire. 

2 

106.6  X  10,000 

R  =  —  — =0.08  ohms  per  wire. 

(108.5)' 

9.08 

Resistance  per  1,000  feet  of  wire  =—  =0.0492.  This  cor- 
responds most  nearly  to  a  No.  oooo  wire.  Adopting  this,  the  re- 
sistance per  i  ,000  feet  of  wire  is  0.04893  and  its  total  resistance  is 
0.04893  X  184.5  =  9  ohms. 

Energy  loss  per  wire  =  I2  R  =  (io8.5)2  X  9=  106,000  watts. 

Energy  loss  per  circuit  =  3  X  106  =  318  K.W. 

Energy  loss  both  circuits  =  2  X  318  =  636  K.W. 

Resistance  drop  per  wire  =  I  R  =  108.5  *  9  =  97^  volts. 

Reactance  volts,  computed  by  factor  from  table  as  follows: 

Reactance  volts  per  1,000  feet  of  transmission  distance  for  each 
ampere  of  current  in  a  wire  No.  oooo  size,  with  a  separation  of  24 
inches  and  a  frequency  of  60  cycles  is,  from  the  table,  0.225. 

Reactance  volts  per  1,000  ft.  for  108.5  amperes  =108.5  x 
0.225  =  24.2  volts.  Reactance  volts  for  184.500  ft.  =  184.5  X 

24.2  =  4,460  volts.    Reactance  volts  for  25  cycles  =-' X  25  = 

60- 

i, 860  volts. 


110       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

This  value  is  for  a  double  circuit,  and  in  calculating  a  three- 
phase  transmission  only  one  leg  is  considered.  Obviously,  the  re: 
actance  volts  are  half  the  amount  per  leg  of  the  reactance  volts  for 

1,860 

a  double  circuit.     Hence  reactance  volts,  actual  will  be  -    -  =  930 

2 

volts. 

Volts     drop  =  V  (Resistance    drop)2     +     (Reactance    volts)2; 

in  this  case  =  V(976)2  +   (93o)2  =  1,272  volts. 

Apparent  energy  lost  in  line  =  1,272  X  108.5  =  138  K.V.A.  per 
wire.  Total  for  the  six  wires  of  the  two  circuits  is  equal  to  6  X  138 
=  828  K.V.A. 

Actual  energy  delivered  by  the  step-up  transformers  to  the  line 
=  actual  energy  delivered  to  step-down  transformers  +  line  loss 
=  8,247  +  636  =  8,883  K.W. 

Apparent  energy  delivered  by  step-up  transformers  is  the  ap- 
parent energy  delivered  to  the  step-down  transformers  +  appar- 
ent energy  of  the  line  =  9,36i  +  828  =  10,189  K.V.A. 

Actual  energy  delivered  to  step-up  transformers  =  energy  given 

8,883 

out  by  them  divided  by  their  efficiency  =—    -  =9,100  K.W. 

0.97 

The  apparent  energy  input  to  the  step-up  transformers  = 
apparent  energy  delivered  by  them  divided  by  their  efficiency  = 

^-10,500  K.V.A. 

0.97 

This  last  is,  of  course,  the  apparent  energy  supplied  by  the 
generators  and  must  be  the  generating  capacity,  while  the  actual 
energy  delivered  by  the  generators  is  9,100  K.W. 

Summarizing  the  computations: 


Size  of  generating  equipment  .............  JOjSoo  K.V.A. 

Size  of  step-up  transformers  ..............  10,189  K.V.A. 

Size  of  step-down  transformers  ...........  9,091  K.V.A. 

Line  wire  —  two  circuits  of  three  wires  each, 

size  B.  &   S.   gauge  ......................  No.   oooo 


TRANSMISSION   CONDUCTORS  III 

Total    loss    in    system  from    generator    to 

motors  =  9,  100  --  8,000  ...............    1,100  K.W. 

Current  in  each  wire  .....................    108.5  amps. 

Effective  voltage  of  step-up  transformers  =  14,  400  +    1,272  = 


Voltage  between  wires  at  step-up  transformers  =  15,672  X 
1.732  =  27,200. 

If  two  pole  lines  each  cam-ing  two  circuits  were  run,  the  load 
would  thus  be  divided  among  four  circuits,  and  the  size  of  each 
wire  would  be  halved.  The  resistance  drop  would  be  the  same, 
but  the  reactance  drop  would  be  diminished  about  half  because 
only  half  the  current,  as  before  computed,  would  flow  in  each  line, 
and  the  calculations  show  that  the  amount  of  the  reactance  volts 
depends  on  the  current  flow.  Also,  a  wire  as  large  as  No.  oooo 
is  heavy  and  difficult  to  erect.  Therefore,  for  this  and  other  prac- 
tical reasons  that  make  desirable  a  double  pole  line,  it  would  be 
better  to  run  four  circuits,  two  on  each  pole  line. 

The  turbine  power  required  is  based  on  the  actual  energy  — 
9,100  K.W.  —  delivered  by  the  dynamo,  and  is  computed  exactly 
as  in  the  preceding  example. 

When  step-up  transformers  are  omitted,  the  calculation  is  some- 
what simplified.  The  use  of  these  transformers  is  a  question  which 
must  be  settled  for  each  case.  Their  advantages  are  :  the  use  of  a 
low-tension  dynamo,  the  use  of  low-voltage  switching  and  manipu- 
lating apparatus,  confining  the  high-voltage  currents  in  an  iron 
case  filled  with  insulating  oil,  and  decreased  cost  of  line  copper. 
Their  disadvantages  are  :  initial  cost,  the  addition  of  a  weak  point  in 
the  circuit,  and  the  continual  power  loss  which  attends  their  opera- 
tion. 

Frequently,  it  is  better  to  use  a  6,6oo-volt  generator,  omit  the 
transformers,  and  with  the  money  thus  saved  add  to  the  quantity 
of  copper  or  even  spend  a  little  more  for  the  wire.  It  is  better 
to  invest  money  in  a  staple  commodity  like  copper,  which  does 
not  depreciate  and  always  has  a  market  value,  than  to  invest 


112       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

in  electrical  apparatus,  when  the  differences  in  initial  cost  and 
operating  losses  are  slight.  The  question  of  the  transmission 
system  is  more  a  financial  than  an  electrical  problem,  and  must  be 
solved  on  the  former  basis. 

The  foregoing  calculations  may  be  summarized  in  formulas 
as  follows: 

Let  E  =  voltage  at  receiving  end  between  wires. 
"    E0  =  voltage  at  station  end  between  wires. 
"    I  =  current  in  line. 
"    F  — power  factor. 
"    D=  distance  of  transmission  in  thousands  of  feet  =  (dist. 

in  miles  X  5,280  -r-  1,000). 
"    N=frequency  of  system  in  cycles  per  second. 

M  =  efficiency  of  step-down  transformers. 
"    Mx  =  efficiency  of  step-up  transformers. 
"    P  =  percentage  energy  loss  in  the  line  -H  100,  referred  to 

delivered  power. 

R  =  resistance  of  each  wire  of  a  circuit  per  1,000  feet. 
"    S  =  reactance  volts  in  line. 
"    K.W.  =  actual  energy  delivered. 
Then  for  a  single-phase  system: 

K.W. 

Energy  to  step-down  transformers.  =  —    — (i) 

M 

K.W. 

Apparent  energy  to  step-down  transformers  =  - (2) 

J\-L  X  -T 

K.W.  X    1,000 
MXFXE    '" 

K.W.  X  1,000  X  P 

— — (in  ohms  per  i  ,000  feet  of  wire) (4) 

2   X    i-J  X  1 

Resistance  drop  =  I  X  R  X  2D (5) 

Q  X  I  X  D  X  N 
Reactance  drop  =  —         — (6) 

Q  being  the  factor  from  the  table  for  the  size  of  wire  adopted 
and  the  distance  of  separation  between  wires. 


TRANSMISSION   CONDUCTORS  113 


Line  drop  =  v  (resist,  drop)2  +   (react,  drop)2 (7) 

Energy  delivered  in  K.W.  by  step- up  transformers 

K.W. 

+  I2  X  R  X  2D (8) 

Energy  delivered   in   K.W.   to   step-up   transformers  =  energy 

K.W.         I2  X  R  X   2D 

delivered  by  generators  =  —  -    (o) 

M  X  M!         Mj  X  1,000 

Apparent  energy  in  K.W.  delivered  by  step-up  transformers 

K.W.        I  X  line  drop 

•+-  - (10) 


M  X  F  1,000 

Apparent  energy  delivered   by  generators   to  step-up  trans- 

K.W.  I  X  line  drop 

formers  =  -+-  — (n) 

M  X  Mt  X  F         1,000  X  Mt 

E.  =  E  +  line  drop  (approximately) (12) 

For  three-phase  lines  the  formulas  become: 

Energy   to  step-down  transformers  =        - (i) 

M 

Apparent  energy  to  step-down  transformers  = (2) 

jyi  /\  .r 

K.W.  X   1,000  E 

I  =  —  -  =  in  which  Ep  = =  effective   voltage. 

3  X  M  X  F  X  Ee  1.732 

K.W.  X  1,000  X   P 
R=         3XDXP 
This  result  is  in  ohms  per  1,000  feet  per  wire. 
Resistance  drop  =  I  X  R  X  D (15) 

Q  X  I  X  D  X  N 

Reactance  drop  = — (16) 

120 


Line  drop  =  ^/(resist,  drop)2  -I-  (reac.  drop)2 
Energy  delivered  by  step-up  transformers 

K.W.  .  3(PXRXD) 

~'  - 


8 


114       DEVELOPMENT   AND   DISTRIBUTION  OF   WATER   POWER 

Energy  delivered  to  step-up  transformers 
K.W.        3(FXRXD) 


M  X  Mt  M!  X    1,000 

Apparent  energy  delivered  by  step-up  transformers 

K.W.          3  (I  X  line  drop) 

-^  +  -  —..... (20) 


Apparent    energy    delivered    to    step-up   transformers 
K.W.  3  (I  X  line  drop) 


M  X  M!  X  F  1,000  X 

E0  =  E  +  line  drop  (approximately)  ................  ____  (12) 

All  the  foregoing  are  simply  close  practical  approximations 
which  are  as  near  to  the  exact  figures  as  standard  sizes  of  wire  and 
electrical  apparatus  make  it  necessary  to  come.  The  effect  of 
capacity  has  been  neglected  as  it  is  negligible  except  in  very  long 
lines  —  say  50  miles  and  above  —  unless  the  separate  wires  of  the 
circuit  are  placed  close  together,  and  good  practice  prevents  this 
closeness  of  conductors.  The  effect  of  the  capacity  current  is  to 
reduce  slightly  the  apparent  energy  and  the  line  current.  It  has 
no  effect  on  the  actual  energy  delivered. 

If  systems  are  installed  on  the  basis  of  the  foregoing  formulas 
and  the  lines  are  long,  the  only  noticeable  result  will  be  a  slightly 
less  line  drop  and  less  heating  of  generators  and  transformers 
than  the  computations  show. 

Aluminum  Conductors.  Aluminum  is  now  used  to  a  limited 
extent  for  transmission  lines.  Its  weight  is  0.3  that  of  copper  for 
a  given  size  and  length  of  wire.  Its  conductivity  is  0.63  that  of 
copper.  Therefore,  for  a  given  resistance  per  mile,  the  area  of  an 

aluminum  wire  should  be  •  -  =1.587  times  the  area  of  a  copper 

0.63   - 

wire.  As  the  area  is  proportional  to  the  square  of  the  diameter,  the 
diameter  of  an  aluminum  wire  must  be  26  per  cent,  greater  than  the 
diameter  of  a  copper  wire  for  equivalent  conductivity  .__The  'weight 
of  aluminum  compared  to  that  of  copper  for  a  given  conductivity 


TRANSMISSION  CONDUCTORS  115 

0.3 

is  equal  to =0.476;  that  is,  47^  pounds  of  aluminum  are  equal 

0.63 

in  conductivity  to  100  pounds  of  copper.  Therefore,  the  price 
which  may  be  paid  for  aluminum  to  produce  a  given  conductivity 

is  -     —  =  2.1  times  the  price  of  copper.     It  should,  however,  be 
0.476 

bought  at  a  lower  price  than  2.1  X  cost  of  copper,  as  it  is  more 
difficult  to  join  together  and  more  trouble  to  put  in  place,  owing 
to  its  comparative  brittleness  and  softness.  At  1.75  times  the 
price  of  copper  it  will  pay  to  substitute  aluminum. 

The  formulas  and  methods  of  computation  before  given  for 
transmission  lines  apply  equally  to  aluminum  and  copper  conduc- 
tors. The  size  of  the  copper  wire  is  taken  from  the  table  to  corre- 
spond to  the  computed  resistance.  By  adding  26  per  cent,  to  its 
diameter,  or  58  per  cent,  to  the  circular  mils  as  given  for  the  copper 
conductor,  the  size  of  the  equivalent  aluminum  wire  is  found. 
Thus  if  the  computed  resistance  is  .0976  per  1,000  feet,  this  corre- 
sponds (nearly)  to  a  No.  o  copper  wire.  The  diameter  of  a  No.  o 
wire  is  0.340  inch.  Adding  26  per  cent,  this  becomes  0.4384, 
which  corresponds  (nearly)  to  a  ooo  wire.  Likewise,  the  circular 
mils  of  a  No.  o  wire  are  115,600.  Adding  58  per  cent,  to  this,  the 
cir.  mils  are  182,600  which  nearly  corresponds  to  No.  ooo  wire. 
The  computed  size  for  aluminum  is  to  be  used  for  taking  the  reac- 
tance volts  drop  factor  from  the  table. 

Solid  aluminum  wires  are  never  used.  Conductors  of  this 
material  must  always  be  stranded  owing  to  its  unreliability  as  to 
tensile  strength  in  occasional  spots.  Also  its  brittleness  makes 
the  stranded  conductors  desirable. 

Arrangement  of  Wires.  In  the  case  of  several  single-phase  cir- 
cuits, all  fed  from  the  same  source  and  working  in  parallel,  the 
wires  may  be  arranged  on  the  cross-arms  in  any  convenient  man- 
ner. If,  however,  two  separate  circuits  fed  from  different  dyna- 
mos run  on  the  same  pole  line,  the  wires  of  each  circuit  should 
be  placed  as  close  together  as  conditions  will  allow,  and  the  -two 


Il6       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

circuits  separated  as  much  as  possible.  This  is  to  avoid  the  effect 
of  mutual  inductance  between  the  two  circuits  which  will  cause  pul- 
sation in  voltage  that  will  seriously  interfere  with  any  lighting  service. 

A  better  way  is  by  transposing  the  wires,  as  shown  in  Fig.  52, 
which  is  a  plan  view.  As  indicated,  the  wires  of  one  circuit  run 
parallel,  all  the  way  from  the  station  to  the  point  of  distribution, 
while  the  other  circuit  has  the  position  of  its  wires  transposed  at 
the  middle  point  of  the  line. 

In  three-phase  systems,  the  wires  are  usually  placed  in  such  posi- 
tions that  lines  joining  their  centres  form  an  equilateral  triangle, 
as  shown  in  Fig.  53.  Where  a  single  circuit  is  placed  on  one  pole, 


x 


FIG.  52. 

no  transposition  is  necessary.  If  two  circuits  be  put  on  one  pole, 
the  wires  of  one  circuit  should  run  parallel,  the  wires  of  the  other 
circuit  being  transposed  twice  in  the  entire  length  of  circuit,  the 
points  of  transposition  being  at  one-third  and  at  two-thirds  the  total 
distance  from  station  to  distribution  point. 

In  Fig.  5 4. the  upper  two  circuits  illustrate  this  arrangement. 
Fig.  55  shows  the  usual  way  of  placing  two  circuits  on  a  single  pole. 
If  a  third  circuit  be  placed  on  the  same  pole  line  with  the  first  two, 
it  must  be  transposed  three  times  in  the  same  distance  that  the  sec- 
ond circuit  is  transposed  once;  or  the  distance  apart  of  the  trans- 
position points  is  one-ninth  the  total  length  of  the  line.  The  lowest 
circuit  shown  in  Fig.  54  gives  this  transposition  as  related  to  the 
other  two  circuits. 


TRANSMISSION   CONDUCTORS 


117 


All  the  foregoing  is  based  on  the  arrangement  of  the  wires  of 
each  circuit,  so  that  any  wire  is  the  same  distance  from  either  of 
the  other  two,  i.e.,  at  the  apexes  of  an  equilateral  triangle.  If, 
however,  the  three  wires  of  a  circuit  are  all  placed  on  the  same 
cross-arm,  so  that  they  lie  in  the  same  plane,  the  wires  of  each  cir- 


cuit  must  be  transposed.  The  transposition  for  one  circuit  on  a 
pole  is  that  of  the  middle  circuit  shown  in  Fig.  54;  that  is,  two  trans- 
positions in  the  length  of  the  transmission,  one  at  one-third,  the 
other  at  two-thirds  the  distance  from  the  power  station.  A  second 


Il8       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

circuit  on  the  same  pole  would  be  transposed  like  the  lowermost  cir- 
cuit shown  in  Fig.  54;  i.e.,  a  transposition  at  each  one-ninth  of  the 
transmission  length. 

A  certain  tension  should  be  put  on  the  wires  in  stringing  them 


FIG.  54. 

on  the  poles,  and  it  should  be  just  great  enough  to  give  a  definite 
amount  of  sag,  or  dip  below  the  horizontal.   The  sag  is  dependent  on 


ft 


4 


FIG.  55. 

the  length  between  spans  and  the  temperature  at  the  time  of  setting. 
A  good  rule  is  to  allow  a  sag  equal  to  0.0155  x  length  between 


TRANSMISSION   CONDUCTORS  1 19 

spans  for  a  temperature  of  60°  F.  Increase  or  diminish  the 
amount  of  sag  thus  found  ;J  per  cent,  for  each  10°  F.  above 
or  below  60°.  Thus,  if  spans  are  200  feet,  the  sag  would  be 
200  X  0.0155  =  3.10  feet  for  60°  F.  If  the  temperature  at  the 
time  of  erecting  were  90°  F.,  the  sag  would  be  increased  by  a 
percentage  =  (90  —  60)  X  7^  =  22^  per  cent. 

22 \  per  cent,  of  3.10  =  0.6975.  Sag  actual  =  3.io  +  0.6975  = 
3.795,  say  3.8  feet  =  3  feet  9^  inches. 

The  spacing  apart  of  wires  varies  from  36  inches  in  short  spans 
—say  up  to  150  feet — to  78  inches  in  long  spans  and  with  high 
voltages.  Increasing  the  distance  of  separation  increases  the  in- 
ductive drop,  thereby  increasing  the  size  of  generators  and  the 
line  losses,  while  if  placed  too  near  together,  the  chance  of  swaying 
bringing  the  wires  in  contact,  or  the  possibility  of  sudden  high  po- 
tentials, due  to  surging,  causing  a  break-down  at  the  cross-arms, 
is  increased. 

Roughly,  in  transmissions  up  to  10,000  volts  the  distance  should 
be  30  to  40  inches,  up  to  30,000  volts  the  separation  should  be  48 
to  60  inches,  and  above  30,000  volts  the  distance  should  be 
about  66  to  72  inches.  These  distances  vary  somewhat  with  the 
length  of  span. 


CHAPTER  X. 
POLE  LINE  AND  ACCESSORIES. 

Supporting  Poles. 

THERE  is  considerable  controversy  as  to  the  best  method  of  sup- 
porting the  transmission  wires.  In  all  electrical  lines  worked  at 
high  voltages,  every  point  of  support  is  a  possible  source  of  trouble 
from  leakage  or  break-down  of  the  insulators.  On  this  account 
the  supports  should  be  placed  far  apart. 

On  the  other  hand,  the  greater  the  distance  between  supports, 
the  greater  is  the  strain  on  the  wires  and  insulators,  the  sag  is  in- 
creased, the  wires  must  be  placed  farther  apart  to  prevent  touching 
when  swayed  by  winds,  and  this  increases  the  inductive  drop. 
Therefore,  the  spacing  of  poles  or  towers  to  carry  the  wires  must  be 
a  compromise  between  these  two  opposing  sets  of  conditions. 

In  cold  climates,  the  poles  must  be  nearer  together  than  in 
milder  latitudes  because  of  the  possibility  of  an  ice-coating  forming 
on  the  wires.  This  may  become  so  thick  as  to  form  a  continuous 
cylinder  having  a  diameter  as  much  as  i  J  inches  greater  than  that 
of  the  wire  itself.  Such  a  mass  of  ice  adds  greatly  to  the  weight 
carried  on  the  poles,  and  may  cause  breaking  of  insulator  pins  or 
rupture  of  the  wire  itself. 

The  standard  practice  in  the  Eastern  States,  for  pole  lines,  is 
about  i5o-foot  spacing,  or  36  poles  per  mile.  In  California  and 
other  Western  States  having  mild  temperatures,  spans  up  to  500 
feet  are  being  used.  These  conductor  lengths  are  too  heavy  to 
carry  on  poles,  and  steel  towers  are  substituted,  which  are  made 
of  ordinary  structural-steel  shapes,  and  weigh  about  i  ,400  pounds  for 
a  45-foot  height,  with  cross-arms  made  of  wrought-iron  pipe,  and 
proper  provision  for  receiving  insulator  pins.  Their  present  cost  is 


POLE   LINE   AND   ACCESSORIES  121 

about  3  J  cents  per  pound,  or  a  45 -foot  tower  placed  in  position  costs 
about  $50.00.  There  are  21  of  these  in  two  miles,  making  the  cost 
$1,050.00,  or  $525.00  per  mile.  Wooden  poles  of  the  same  height 
and  proper  diameter  cost  with  cross-arms  about  $7.50  each,  set. 
Thirty-six  of  these  for  one  mile  cost,  therefore,  $270.00,  or  about  half 
the  cost  of  the  steel  towers.  The  poles,  however,  require  replacing 
within  from  10  to  12  years,  while  the  towers  will  last  indefinitely. 
The  towers  must  be  painted  once  every  1 8  to  20  months,  which  is  an 
item  of  maintenance  expense.  Also,  they  allow  the  wires  to  ground 
if  an  insulator  should  fail.  In  their  favor  are  their  durability  and 
the  distance  apart  of  the  insulators.  Their  chief  drawback  is  the 
first  cost;  and  in  spite  of  theory  and  calculations,  the  main  object 
in  view  when  installing  a  transmission  plant  is  to  get  it  into  effi- 
cient and  reliable  operating  form  as  cheaply  and  expeditiously  as 
possible.  After  dividends  have  been  declared  a  few  years,  and  the 
wooden  poles  need  to  be  replaced,  the  steel  towers,  bought  with 
earnings  of  the  plant,  may  be  erected. 

When  long  spans  are  adopted,  hard-drawn  copper  wires  should 
be  used. 

Poles  may  be  of  nearly  any  kind  of  growth  that  is  strong,  rea- 
sonably straight,  and  resists  rot.  White  cedar,  yellow  pine,  locust, 
chestnut,  cypress,  and  spruce  have  all  been  used. 

White  cedar  and  chestnut  poles  have  an  average  life  of  twelve 
years,  pine  eight,  cypress  fourteen,  and  red  cedar  eighteen  years. 
Concrete  poles  reinforced  by  iron  bars  have  been  lately  tried  and 
found  to  be  satisfactory  in  every  respect  except  the  initial  cost, 
which  is  about  three  times  that  of  wood  poles. 

The  height  of  poles  depends  on  local  conditions.  In  open 
country,  on  a  private  right  of  way,  the  lowest  wires  should  be  at 
least  28  feet  above  the  ground.  In  passing  over  roadways  or  popu- 
lated districts  the  wires  should  be  at  least  45  feet  above  the  ground, 
and  55  feet  is  a  better  height. 

The  length  of  poles  should  be  about  12  J  per  cent,  greater  than 
the  height  above  ground,  which  excess  is  the  length  to  be  set  in  the 
ground.  In  soft  marshy  earths  the  depth  in  the  ground  should 


122        DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

be  greater.  No  pole  should  be  set  with  less  than  four  feet  in  the 
ground. 

Poles  must  be  amply  proportioned  to  carry  the  various  loads 
imposed  on  them  by  the  pull  of  the  wire,  due  to  its  weight  between 
spans,  the  weight  of  the  largest  possible  ice-coating,  the  wind  press- 
ure, and  the  strain  set  up  when  the  direction  of  the  wires  is  changed 
producing  an  unbalanced  pull  on  the  poles.  In  the  last  case 
the  pole  is  braced  by  heavy  guy  wires  running  from  a  point  near 
the  top  of  the  pole  to  a  short  heavy  stub  and  fixed  firmly  in  the 
ground  at  some  distance  from  the  pole. 

The  following  proportions  are  usual  in  practice: 

Poles  35  feet  high  should  have  a  circumference  of  18  inches  at 
the  top,  45 -foot  poles  22  inches,  5  5 -foot  poles  24  inches. 

In  setting  poles,  the  butts  should  be  given  a  good  coating  of  hot 
pitch  or  asphaltum,  if  they  have  been  previously  seasoned.  Green 
poles  should  not  be  so  coated,  however,  as  it  hastens  their  decay 
by  imprisoning  the  moisture  in  an  impervious  covering.  When 
covered  with  pitch,  the  coating  should  extend  up  at  least  a  foot 
above  the  ground  line. 

In  many  cases,  two  separate  pole  lines  have  been  erected  each 
carrying  its  own  circuits,  so  that,  in  event  of  accident  to  either,  it 
can  be  switched  out  of  service  and  repairs  made  while  the  other  line 
carries  the  load,  with  a  greater  drop  and  line  loss.  This  is,  of 
course,  an  excellent  arrangement,  but  its  cost  is  high  and  a  dupli- 
cate pole  line  should  more  properly  be  paid  for  by  earnings  pro- 
duced by  a  single  line. 

Where  the  line  passes  through  wooded  country,  the  trees  on 
either  side  must  be  cut  down,  so  that  no  tree  is  left  near  enough 
to  the  line  to  reach  it  if  uprooted  or  broken  off.  Also  duplicate  pole 
lines  should  be  set  apart  far  enough  to  prevent  a  broken  pole  on 
either  line  from  falling  against  the  other  line. 

Cross-arms.  These  rr^ay  be  of  any  of  the  woods  which  are 
strong  and  durable.  Yellow  pine  is  used  more  than  any  other 
material. 

The  usual  cross-arm  is  a  rectangular  bar  varying  from  2^  X 


POLE   LINE   AND    ACCESSORIES  123 

3J  to  4^  X  6  inches  in  cross-section.  The  upper  surfaces  are 
beveled  to  allow  water  to  run  off  freely. 

They  are  set  in  shallow  recesses  or  gains  cut  in  the  pole,  and 
bolted  on  with  two  bolts  each  of  from  \  to  f  inch  in  diameter, 
which  pass  through  pole  and  cross-arm  and  are  fastened  with  nuts. 
Large  washers  are  put  on  the  bolt  at  each  end  to  make  a  good 
bearing  surface  against  the  wood.  The  arms  are  further  fastened 
by  bracing,  the  usual  form  of  brace  being  a  pair  of  flat  galvanized 
iron  strips  about  \  X  ij  inches  in  cross-section,  with  a  hole  in 
each  end.  One  \  X  5  inch  lag  screw  passing  through  the  holes  in 
the  two  braces,  laid  one  on  top  of  the  other,  holds  these  ends  to  the 
pole.  The  other  ends  are  spread  apart  and  fasten  to  the  cross- 
arm  with  a  \  X  3  inch  lag  screw  through  each. 

A  pole  head  for  a  three-phase  circuit  is  shown  in  Fig.  52  and 
gives  these  details. 

Usually,  cross-arms  are  boiled  in  linseed  oil  for  several  hours 
to  preserve  them,  and  then  painted.  In  any  case  they  should  be 
painted  with  a  good  weather-proof  paint.  One  of  the  best  in- 
vestments is  to  use  large,  strong  cross-arms.  The  large  sizes  cost 
but  little  more  than  the  smaller  ones,  and  one  of  the  weak  points  is 
at  the  cross-arms.  Never  use  a  size  smaller  than  3  J  X  4!  inches. 

Insulators.  There  are  two  prime  requisites  for  any  insulator; 
it  must  have  a  high  insulating  quality  and  it  must  possess  mechan- 
ical strength.  All  the  strains  in  the  line,  the  weight  of  the  wires,  or 
the  stresses  set  up  by  wind  and  swaying  must  be  taken  by  the  in- 
sulators, and  the  element  of  mechanical  strength  is  the  really  im- 
portant factor. 

For  this  reason,  porcelain  insulators  are  preferable  to  glass  ones, 
provided  the  porcelain  is  high  grade  and  well  burned  until  it  is 
vitreous  throughout. 

Glass  insulators,  however,  have  been  used  in  high-tension  trans- 
mission work  up  to  40,000  volts  with  marked  success,  and  their 
lower  cost  makes  them  attractive. 

The  controversy  of  glass  versus  porcelain  which  endured  so  long 
has  practically  been  settled  in  favor  of  porcelain,  due  no  doubt  to 


124       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

improved  methods  of  manufacture  and  the  resulting  betterment 
of  the  quality  of  the  latter.  Some  engineers  still  use  glass,  however, 
and  find  them  satisfactory. 

Types  of  insulators  are  many  and  various,  and  their  descrip- 
tion here  would  be  out  of  place. 

Never  put  an  insulator  in  place  on  a  high-tension  line  without 
first  testing  it  for  dielectric  strength.  The  test  is  standard  and 
simple. 

Invert  a  number  of  insulators  in  a  pan  of  salt  water,  of  sufficient 
depth  to  cover  about  seven-eighths  of  the  insulator.  Fill  the  up- 
turned pin  opening  in  the  centre  of  the  insulator  about  half  full- 
of  salt  water.  Be  sure  that  the  insulator  is  fairly  dry  from  the  sur- 
face of  the  water  in  the  pan  to  the  water  in  the  inner  hollow  of  the 
insulator,  by  wiping  off  spilled  water.  Put  a  metallic  pin  or  a  car- 
bon rod — an  ordinary  arc-lamp  carbon  does  very  well — into  each 
of  the  pin  openings  so  that  it  reaches  to  the  bottom.  Connect  the 
pan  to  one  terminal  of  the  secondary  of  a  transformer,  and  the  rods 
or  pins  to  the  other  terminal.  The  transformer  should  give  a  po- 
tential of  three  to  four  times  that  of  the  line  the  insulators  will  be 
used  on.  Switch  on  the  current  to  the  primary  of  the  transformer. 
Defective  insulators  will  be  ruptured  and  their  pressure  indicated 
by  vicious  arcing.  A  fuse  must  be  placed  in  the  circuit  to  the  pri- 
mary of  the  transformer  to  protect  it  when  the  insulators  give  way. 

To  test  the  quality  of  the  porcelain  in  insulators,  break  one  in 
pieces.  Put  red  ink  on  the  fractures  and  allow  it  to  dry,  then  wash 
the  fracture  thoroughly.  If  the  ink  washes  off  clean,  the  porcelain 
may  be  considered  as  good  quality  and  without  absorptive  power. 
If  the  ink  does  not  wash  off,  the  porcelain  is  not  suitable  for 
Insulating  purposes. 

The  cost  of  high-tension  porcelain  insulators  runs  from  50 
cents  to  $2.00  each.  Glass  insulators  cost  from  10  cents  to  40 
cents  each.  The  use  of  glass  should  be  limited  to  voltages  of 
30,000  volts  or  under. 

Insulator  Pins.  These  are  made  of  both  wood  and  iron. 
Various  kinds  of  woods  are  used,  but  locust  is  the  best. 


POLE   LINE   AND   ACCESSORIES  125 

The  pins  must  be  strong  enough  to  take  the  various  line  strains 
before  set  forth.  Experience  shows  that  the  standard  pin,  having 
a  1 1  inch  diameter  at  the  shank  (i.e.,  the  lower  end,  which  fastens 
into  the  cross-arm),  is  not  sufficiently  strong  to  carry  the  large  wires 
over  long  spans  that  are  now  encountered  in  transmission  work. 
No  wooden  pin  should  be  less  in  diameter  than  2  inches  at  the  shank; 
and  if  the  length  of  the  pin  above  the  cross-arm — that  is,  exclusive 
of  the  shank — should  exceed  n  inches,  the  diameter  should  be 
made  greater.  In  fact,  2}  inches  diameter  for  pins  16  inches 
long  is  not  excessive. 

It  is,  of  course,  understood  that  the  cross-arms  are  of  proper 
thickness,  which  is  2  inches  greater  than  the  diameter  of  the  pin, 
giving  not  less  than  i  inch  of  stock  on  either  side  of  the  pinhole. 
The  length  of  the  shank  should  be  the  same  as  the  depth  of  the 
cross-arm,  so  that  the  shank  passes  through  the  cross-arm  from 
top  to  bottom.  The  pins  are  held  in  their  sockets  by  passing  a 
| -inch  coach  bolt  through  the  cross-arm  and  each  pin  shank. 

Wood  pins  should  always  be  boiled  in  linseed  oil  or  stearic  acid 
for  several  hours  before  putting  in  position. 

There  are  several  varieties  of  iron  pins.  In  one  form  the  pin 
is  made  of  f-inch  rods  threaded  to  screw  into  a  cast-iron  upper 
piece,  which  latter  has  approximately  the  dimensions  of  a  wooden 
pin.  The  insulator  screws  onto  this  casting. 

Another  form  comprises  a  hollow  porcelain  shape,  having 
proper  dimensions  to  fit  into  the  insulator,  an  iron  pin  passing 
through  the  porcelain  piece  and  through  the  cross-arm. 

Wooden  pins  are  subject  to  deterioration  from  charring,  burn- 
ing, and  softening.  The  first  two  come  from  leakage  currents 
which  manage  to  find  a  path  due  to  the  accumulation  of  dust,  dirt 
and  sometimes  moisture.  Softening  is  produced  by  the  "brush 
discharge"  from  the  line,  which  produces  minute  quantities  of 
nitric  acid.  This  eats  into  the  wood  and  destroys  it.  Iron  pins 
are  not  subject  to  any  of  these  troubles,  and  their  superior  strength 
would  seem  to  make  them  the  best  form  of  pin.  They,  however, 
lack  the  insulating  quality  of  the  wooden  pin,  they  are  more  con- 


126       DEVELOPMENT  AND   DISTRIBUTION  OF  WATER   POWER 


ducive  to  leakage  currents  and  insulator  break-downs;  are  more 
expensive  to  install,  and  tend  to  loosen  in  their  sockets  if  the  cross- 
arms  are  of  wood.  Therefore,  the  wooden  pins  are  used  on  the 

majority  of  transmission  lines  in  this 
country.  The  use  of  iron  pins,  how- 
ever, is  increasing,  due  to  the  better 
grade  of  insulators  now  obtainable. 

Insulators  set  on  iron  pins  should 
always  be  held  in  place  with  cement. 
Ordinary  Portland  cement,  made  to  a 
thick  paste  with  water  is  very  good,  or 
melted  sulphur  may  be  used. 

A  recent  method  of  supporting  trans- 
mission conductors  eliminates  the  insu- 
lator pins,  and  suspends  the  wires  below 
the  cross-arms  by  means  of  insulating 
suspension  links.  These  links  are  of 
two  types,  comprising  those  which  are 
meant  to  hang  vertically  and  those  which 
catch  the  end  of  a  wire  and  hold  it  to  the 
pole  and  have  a  horizontal  position  when 
installed. 

Fig.  56  shows  a  series  of  three  of 
these  vertical  suspension  links,  while 
Fig.  57  shows  three  horizontally  stretched 
links,  Fig.  58  being  a  section  through 
i  one  of  the  latter  which  shows  the 
method  of  constructing  these  insulators. 
They  are  made  of  porcelain  discs 

having  spherical-shaped  portions  in  their  centres.  Two  semicir- 
cular tunnels,  at  right  angles  to  each  other  and  interlinked, 
are  formed  in  the  spherical  portion,  one  tunnel  passing  in  one 
from  one  side  of  the  disc  and  back  out  the  same  side,  while  the 
other  tunnel  passes  in  from  the  opposite  side  and  back  out 
on  the  same  side  it  enters.  The  construction  is  clear  from 


FIG.  56. 


POLE   LINE   AND   ACCESSORIES 


127 


the  figures,  and  it  is  obvious  that  the  strain  on  the  porcelain  is 
compressive. 

Figs.  59  and  60  show  the  methods  of  using  these  link  insulators. 
Fig.  59  shows  the  suspension  of  a  wire  hanging  from  a  cross-arm 


FIG.  57. 

and  below  it.  Fig.  60  shows  the  horizontal  or  tension  link  insula- 
tors attached  to  a  supporting  tower,  and  to  which  the  ends  of  the 
transmission  wire  are  fastened.  The  wires  are  in  the  latter  case 
practically  "dead-ended,"  but  the  line  is  made  continuous  by  a 

loose  connecting  wire  which  joins 
the  two  conductors  as  indica- 
ted in  the  figure.  The  preferred 
practice  is  to  use  the  tension  in- 
sulators about  every  mile,  and 
suspension  insulators  at  the  inter- 
mediate supporting  points.  This 
produces  independent  sections  of 
wire,  each  one  mile  in  length, 
supported  at  proper  intervals. 

With    these    insulators    any 
practical  attainable  voltage  may 
FlG     g  be  used,  as  each  disc  is  capable 

of  carrying   25,000  volts  with  a 

factor  of  safety  against  arcing  around,  from  one  face  to  the  other 
of  about  -2^  For  higher  voltages  the  insulators  are  simply  placed  in 


128       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 


series,  two  being  required  for  50,000  volts  or  four  for  100,000  volts. 
Owing  to  their  great  strength  which  enables  each  insulator  to  sup- 
port a  load  of  three  tons  without  rupture,  the  weight  of  wire 


FIG.  59. 


FIG.  60. 


between  spans,  and  consequently  the  length  of  spans,  may  be 
very  great.  Ten  poles  or  towers  per  mile  is  the  spacing  that  has 
been  adopted  for  one  transmission  line  using  these  insulators, 

and  spans  up  to  1,000  feet  in 
length  may  be  safely  carried. 

The  diameter  of  the  discs 
is  10  inches  for  25,000  volt  un- 
its and  6J  inches  for  12,000 
volt  units.  If  the  porcelain 
should  crush  or  be  otherwise 
shattered,  the  line  does  not 
fall,  as  the  interlinked  wire 
loops  passing  through  the  tun- 
nels in  the  porcelain  simply 
come  together  and  take  the 
strain.  Fig.  61  shows  a  broken 
insulator  and  the  resulting 
linking  together  of  the  wire 
loops.  Fig.  62  shows  in  outline  the  arrangement  of  two  three- 
phase  circuits  on  a  tower,  the  voltage  being  100,000.  The  wires 
are  not  arranged  triangularly  and  therefore  must  be  transposed, 


FIG.  61. 


POLE    LINE   AND   ACCESSORIES 


I29 


as  directed  in  the  previous  chapter,    in  order  to  balance  static 
and  inductive  effects. 

Fig.  63  shows  the  general  layout  of  a  two-circuit,  three-phase 
line  for  80,000  volts,  the  wires  being  placed  in  a  right  triangular 
relation,  so  that  the  inductive  effects  are  approximately  balanced. 


END  ELEVATION 


SIDE  ELEVATION 

FIG.  62. 


HOR.  SECTION  Q-H 


The  advantages  over  the  ordinary  pin-and-insulator  construc- 
tion claimed  for  this  system  of  supporting  wires  are  : 

(a)  With  the  standard  type  of  pin  insulator  now  used,  the 
difficulties  of  construction  increase  very  rapidly  at  the  higher 
voltages.  The  cost  of  insulator  for  a  given  margin  of  safety  in- 
creases for  voltages  above  60,000  nearly  as  the  cube  of  the  increase 
in  voltage.  Either  very  large  petticoat  diameters  must  be  used 
or  very  high  insulators  with  many  petticoats.  In  either  case  the 
9 


130       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 


manufacture  of  the  porcelain  parts  is  a  difficult  and  expensive 
matter;  and  with  the  long  pin  necessary,  the  mechanical  stresses 
from  the  line  on  insulator,  pin,  and  cross-arm  are  objectionable. 
With  the  series  unit  system  here  proposed,  the  cost  of  insulators 


HOR.  SECTION  A-B 


i''3[-n j; 

.  £H  i 


.  HOR.  SECTION  C-D 
Lightning  Arrester  Wire 

Clamp  forx'j 
Ground  Wire 
"  Diam. 


Sketch  Showing 
Attachment  of 
Wires  to  Prevent 
Creeping 


I"  i.3 

END  ELEVATION 


SIDE  ELEVATION 


FIG.  63. 


progresses  only  in  direct  proportion  to  the  increase  in  voltage,  the 
only  change  being  in  the  number  of  units  in  series.  There  is 
practically  no  limit  to  the  degree  of  insulation  obtainable. 

(b)  One  of  the  most  difficult  elements  of  design  in  a  trans- 
mission tower  where  long  pins  and  petticoat  insulators  are  used  is 
to  obtain  a  cross-arm  which  will  resist  the  torsional  stresses  due 


POLE   LINE   AND   ACCESSORIES  13! 

to  the  leverage  of  the  pin.  With  the  pin  entirely  eliminated,  the 
stresses  are  directly  applied  to  the  cross-arm;  this  cheapens  the 
construction  of  the  tower. 

(c)  In  the  arrangements  shown,  where  the  insulating  units  are 
attached  on  either  side  of  the  cross-arm,  taking  the  full  tension 
in  the  line  with  jumper  connections  between  spans,  the  insulation 
can  be  increased  indefinitely  by  adding  discs  in  series  without  in- 
creasing the  space  occupied  on  the  tower. 

(d)  Where  each  span  is  dead-ended,  as  in  (c),  all  faces  of  the 
insulating  units  are  exposed  to  the  cleansing  action  of  the  rain, 
so  that  dirt  cannot  accumulate  thereon.     This  arrangement  also 
prevents  the  dripping  water  from  forming  electrical  communication 
between  units,  as  occurs  from  one  petticoat  to  another  in  the  pin 
type  of  insulator. 

(e)  A  standard  insulating  unit  can  be  adopted   for   all  volt- 
ages, the  only  variation  being  in  the  number  linked  in  series. 

(f)  If  any  insulating  unit  becomes  damaged    or    completely 
shattered,  the  insulation  of  the  remainder  is  not  affected.     The 
damaged  unit  can  be  replaced  without  the  necessity  of  renewing  the 
whole. 

(g)  If  a  tower  is  directly  struck  by  lightning,  the  cross-arms 
will  be  likely  to  take  the  discharge,  since  they  are  above  the  lines, 
whereas  in  the  pin  type  of  insulator  the  line  is  usually  the  highest 
point. 

(h)  In  long-span  installations,  where  the  conductor  at  each 
end  of  the  span  is  tied  fast  to  an  insulator  mounted  on  a  pin, 
experience  has  shown  that  crystallization  is  apt  to  take  place  in 
the  conductor  and  the  tie,  due  to  its  rigidity  at  that  point  and  the 
vibrations  in  the  span.  This  frequently  results  in  breakage  of  the 
conductor.  The  flexible  connection  between  conductor  and  cross- 
arm  afforded  by  the  series  of  insulators  should  reduce  this  tendency 
to  crystallization,  and  should  therefore  permit  spans  of  any  length 
to  be  used  without  further  precautions  against  this  action. 

It  might  appear  that  with  the  conductor  suspended  under  the 
cross-arm,  serious  swinging  to  and  fro  would  take  place.  From 


132       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

numerous  observations  it  is  believed  that  no  such  swinging  will 
occur.  Long  aerial  spans  under  wind  pressure  take  a  permanent 
and  steady  deflection  throughout  the  span  proportional  to  the 
average  wind  velocity  along  the  span,  and  no  indications  have 
been  observed  of  long  spans  responding  to  gusts.  The  towers 
are  designed  so  that  the  conductor  can  safely  be  deflected 
by  the  wind  about  sixty  degrees  on  either  side  of  the  neutral 
position. 

Exit  jrom  Power -house.  Where  the  high-tension  wires  leave  the 
power-house,  they  must  pass  through  the  wall  or  roof  in  such  a 
manner  as  to  avoid  the  possibility  of  touching  any  part  of  the 
structure,  and  the  ingress  of  rain  is  prevented. 

Several  excellent  methods  have  been  devised  for  the  exit  of  the 


FRONT  VIEW 


FIG.  64. 

line  wire.  One  is  shown  in  Fig.  64  which  is  suitable  for  voltages 
up  to  30,0x30  volts. 

Tile  pipes  12  inches  in  diameter,  and  spaced  14  to  16  inches 
between  centres,  are  set  in  the  walls  sloping  downward  from  in- 
side to  outside,  as  shown.  The  slope  may  vary  from  twenty  to 
thirty  degrees  to  the  horizontal. 

The  wire  passes  from  insulator  A  inside  the  station,  through 
the  tile  pipe,  to  insulator  B  outside  the  station,  the  positions  of  the 


POLE  LINE  AND  ACCESSORIES 


133 


insulators  being  fixed  to  keep  the  wire  in  the  centre  of  the  pipe. 
The  downward  slope  of  the  wire  is  to  prevent  water  on  the  wires 
from  draining  into  the  power  station. 

Another  excellent  arrangement  is  that  shown  in  Fig.  65. 

The  roof  of  the  power-house  is  extended  out  about  four  feet 
beyond  the  wall,  and  a  small  box- like  room  is  built  below  this  ex- 


Transfonners 


FIG.  65. 

tension,  as  indicated.  Holes  in  the  wall — one  hole  for  each  wire, 
the  diameter  being  12  to  14  inches — allow  the  wires  to  pass  from 
the  interior  of  the  station  into  this  compartment.  The  floor  or 
bottom  of  the  compartment  has  holes  in  it  so  that  the  wires  may 
be  turned  downward  and  carried  out  through  them.  Two  pairs 
of  insulators  or  brackets  serve  to  support  and  guide  the  direction 
of  the  wires.  The  compartment  further  serves  as  an  enclosure 
for  the  lightning  arresters,  which  are  installed  as  shown. 


134       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

Other  methods  involving  the  use  of  openings  covered  with  glass 
plates,  each  plate  having  a  small  hole  in  it  for  the  wire  to  pass 
through,  have  been  used.  There  is,  however,  always  danger  of 
dirt  and  dust  collecting  on  the  plates  and  providing  leakage  paths. 
The  general  opinion  now  is  that  a  simple  hole  of  twelve  to  six- 
teen inches  diameter  is  the  best  construction. 


CHAPTER  XI. 
LIGHTNING  PROTECTION. 

UNDER  the  general  classification  "lightning  arresters"  come  all 
that  class  of  devices  for  protecting  a  line  and  the  machinery  at 
each  end  of  it  from  sudden  excessive  potentials.  These  may  arise 
from  lightning  striking  the  line,  or  any  atmospheric,  electrical  dis- 
turbance that  causes  a  high  potential  to  build  up  between  the  line 
and  the  earth.  Also,  static  charges,  resonance  effects,  and  surging 
produced  by  abnormal  conditions  in  the  line  may  produce  a  high 
potential  the  action  of  which  is  similar  to  that  of  atmospheric  dis- 
turbances. These  potential  differences  cause  discharges  tending 
to  equalize  themselves,  and  in  every  case  the  charges  may  be  dis- 
sipated by  a  connection  of  the  line  to  the  earth.  Unless  some  path 
is  provided  for  them,  they  wrill  go  as  near  to  earth  as  possible  by 
the  route  of  least  resistance,  i.e.,  the  machinery,  and  jump  through 
insulation  and  air  to  ground,  and  in  their  passage  will  melt  wires 
and  destroy  the  insulation. 

Also,  lightning  splinters  poles  and  cross-arms  and  breaks  in- 
sulators. 

To  prevent  the  line  potential  from  rising  to  an  excessive  value 
above  that  of  the  earth,  barbed  wire  strung  on  insulators  on  the 
same  pole  line,  above  the  transmission  wires,  has  been  used.  The 
barbed  wire  is  well  connected  to  earth  about  every  quarter  of  a  mile. 
The  barbs  offer  multitudinous  points  for  the  discharge  of  static 
electricity,  and  they  are  always  at  the  potential  of  the  earth  because 
of  the  numerous  ground  connections.  Therefore,  the  region  sur- 
rounding the  wires  of  the  line  are  kept  continually  at  the  same 
potential  as  the  earth. 

This  arrangement,  while  helpful,  does  not  alone  meet  the  neces- 

135 


136       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER  POWER 

sities  of  the  case,  and  in  addition  to  it  other  forms  of  lightning 
arresters  must  be  installed. 

The  standard  lighting  arrester  now  in  use  is  made  up  of  a  num- 
ber of  small  knurled  metallic  cylinders,  set  side  by  side  in  a  por- 
celain frame  and  separated  from  each  other  by  small  air  gaps.  A 
cylinder  at  one  end  of  the  group  is  connected  to  the  line  ;  the  cylinder 
at  the  other  end  is  connected  to  the  ground.  The  air  gaps  prevent 
the  normal  line  potential  from  sending  current  to  the  earth  by  this 
path,  but  excessive  potentials  will  jump  the  gaps  from  cylinder  to 
cylinder  until  the  ground  wire  is  reached. 

In  order  to  make  these  arresters  effective,  there  must  be  some 
device  to  oppose  the  rush  of  discharges  to  the  station  and  compel 
them  to  take  the  path  to  the  ground  through  the  lightning  arresters. 
Choke  coils,  or  flat  coils  of  copper  wire  or  ribbon  which  have  a 
copper  area  sufficient  to  carry  the  line  current  easily,  present  a 
barrier  to  the  passage  of  lightning  or  other  high-frequency  dis- 
charges. The  inductance  of  the  coils  creates  but  little  opposing 
voltage  to  the  line  current,  of  25  to  60  cycles  per  second  frequency, 


Choking  Coils 


Transformers 


but  in  the  case  of  oscillatory  discharges,  where  the  frequency  may 
run  up  into  the  millions,  the  opposition  to  the  passage  of  such  dis- 
charges is  so  great  that  the  path  through  the  arrester  air  gaps  is 
the  easier. 

Fig.  .66  shows  the  connections  for  lightning  arresters  and  choke 


LIGHTNING   PROTECTION  137 

coils,  between  the  transformers  or  generator  and  the  line.  The 
arresters  are  each  connected  on  one  side  to  a  line  wire,  and  on  the 
other  side  to  the  earth. 

Lightning  arresters  are  almost  valueless  without  choke  coils. 

A  form  of  combined  lightning  arrester  and  choke  coil  is  dc- 


FIG.  67. 

picted  in  Fig.  67.     This  has  been  successfully  used  in  Europe,  and 
possesses  certain  advantages. 

It  comprises  several  cast-iron  shapes,  shells,  and  diaphragms 
which  when  assembled  together  form  an  egg-shaped  structure  as 
shown.  These  several  cast-iron  parts  are  connected  together  by 
copper  wires,  the  various  sections  being  in  series.  From  the  last 
section  on  one  side  a  connection  is  made  to  the  choke  coil,  and  from 
the  other  terminal  of  the  choke  coil  the  wire  passes  to  the  dynamo. 
The  line  wire  is  attached  to  the  first  of  the  cast-iron  sections. 
Near  the  ends  of  the  structure  are  placed  horn-shaped  pieces  of 
metal,  the  distance  of  separation  between  the  end  and  the  horn- 
shaped  piece  being  adjusted  to  form  a  discharge  air  gap,  the  latter 
pieces  being  connected  to  the  ground  as  shown.  The  current  from 
the  dynamo  passes  through  the  choke  coil,  thence  to  the  cast-iron 
piece  connected  to  it,  then,  by  means  of  the  short  connecting  wire, 
to  the  next  cast-iron  piece,  and  so  on  until  it  reaches  the  line.  The 
electrical  resistance  of  the  device  is  so  small  as  to  be  negligible,  and 


138       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 


the  inductance  of  the  choke  coil  is  low,  so  that  but  little  opposition 
is  offered  to  passage  of  the  normal  station  count.  When,  however, 
a  sudden  charge,  seeking  earth,  comes  in  over  the  line,  it  spreads  over 
the  large  surface  presented  by  the  shell  and  tends  to  charge  it 
electrostatically,  which  condition  causes  a  concentration  of  potential 
at  the  pointed  ends  of  the  shell  also.  The  rapid  passage  from  cast 
iron  to  copper,  again  to  cast  iron,  and  to  copper,  and  so  on  through 
the  several  sections  of  the  shell,  combined  with  the  action  of  the 
choke  coil,  sets  up  a  strong  retarding  action  to  the  passage  of  high- 
frequency  currents,  which  compels  the  charge  to  pass  across  the 
air  gaps  to  the  horn-shaped  pieces  and  thence  to  earth. 

Another  good  form  of  lightning  arrester  is  known  as  the  horn 


K 


A 


Ground 


FIG.  68. 


type.  This  is  made  of  ordinary  copper  wire  size  No.  ooo,  bent 
in  the  form  shown  in  Fig.  68.  Two  of  these  bent  pieces  supported 
on  insulators  form  an  arrester;  one  horn  is  connected  to  a  line  wire, 
while  the  other  is  connected  to  the  ground  through  a  fuse. 

The  dimensions  given  in  the  figure  are  those  for  a  50,000- volt 


LIGHTNING   PROTECTION 

system.     For  smaller  potentials  the  air  gap  between  the  horns  is 
correspondingly  diminished. 

A  simple  and  effective  form  of  arrester  used  in  Europe  com- 
prises a  plate  of  copper  attached  to  each  of  the  line  wires  against 
which  a  small  stream  of  water  is  thrown  from  a  nozzle.  The  re- 


Horn. Lightning 
.  Arreste 


To 


To  Transformer 
Choking  Coils 


TIG.  69. 

sistance  of  the  water  is  too  high  to  allow  any  appreciable  leakage 
of  current,  but  forms  a  good  path  for  lightning  or  static  discharges. 

To  thoroughly  protect  a  line  there  should  be  installed  two 
choke  coils  in  series  with  each  wire,  and  two  different  forms  of 
lightning  arresters  attached  to  the  line  next  to  the  outer  choke  coil, 
and  two  more  arresters  of  different  types  installed  between  the  choke 
coils;  and  this  arrangement  should  be  duplicated  at  both  ends  of  the 
line.  Fig.  69  indicates  this  method  of  protection,  using  standard 
cylinder  arresters  and  horn  arresters,  a  single  wire  only  of  the  cir- 
cuit being  shown. 

In  long  lines  standard  or  horn  arresters  should  be  placed  every 
two  or  three  miles  along  the  line,  the  distance  apart  depending  on 
the  frequency  and  violence  of  thunder-storms  and  other  atmos- 
pheric electrical  disturbances. 

In  regions  where  such  phenomena  are  frequent,  it  is  advisable 
to  use  the  overhead  barbed  wire,  before  described,  in  addition  to 
the  lightning  arresters  along  the  line. 

Unless  the  ground  connections  are  all  well  made  to  some  point 
which  is  continuously  damp,  they  will  not  form  the  required  low- 


140       DEVELOPMENT   AND    DISTRIBUTION   OF   WATER   POWER 

resistance  path  to  earth.  If  it  is  necessary  to  locate  them  where 
the  ground  is  always  dry,  a  small  water  pipe  should  lead  to  the 
earth  at  the  ground  connection  and  enough  water  allowed  to  con- 
stantly drip  to  keep  the  place  damp.  The  ground  connection  to 
the  arrester  may  be  made  by  connecting  to  water  pipes  where 
they  are  two  inches  in  diameter  or  greater;  in  other  cases  copper 
plates  not  less  than  two  feet  square  and  one-sixteenth  inch  in  thick- 
ness should  be  sunk  in  the  ground  to  a  depth  of  five  feet  or  more, 
depending  on  the  depth  at  which  permanent  dampness  is  reached. 
Coke,  broken  into  fine  particles,  is  packed  on  either  side  of 
the  plate,  the  thickness  of  the  coke  being  at  least  six  inches;  the 
ground  wire  is  securely  soldered  or  brazed  to  the  plate  and  carried 
straight  upward  to  the  ground  terminal  of  the  arrester.  The  ground 
wire  should  be  No.  oo  solid  copper.  If  possible  there  should  be 
no  bends  in  it  whatever;  and  if  there  are  more  than  two  ninety- 
degree  bends  in  it,  its  efficiency  will  be  impaired. 


CHAPTER  XII. 
SWITCHING  AND  CONTROLLING  APPARATUS. 

ALL  switches  for  potentials  above  2,000  volts  should  be  of  the 
kind  that  have  their  blades  and  clips  submerged  in  oil  and  known 
as  oil  switches.  The  switches  themselves  are  placed  back  of  the 
switchboard,  and  manipulated  from  the  front  by  means  of  handles 
that  pass  through  the  board  to  the  front,  and  which  connect  by 
rods  or  links  with  the  switching  mechanism.  In  some  cases  the 
switches  are  placed  on  the  wall  in  the  rear  of  the  switchboard,  the 
handles  being  on  the  front,  and  connecting  by  links  or  rods  to  the 
switches.  A  standard  switch  of  this  type  is  shown  in  Fig.  70. 

This  arrangement  is  suitable  for  pressures  up  to  10,000  volts. 
Above  this,  the  switches  should  be  placed  in  brick  or  concrete 
chambers  beneath  the  switchboard  and  worked  by  handles  on  the 
board  mechanically  connected  to  the  switch  gear.  In  the  case  of 
large  switches  for  high  potentials,  the  switch,  instead  of  being  moved 
directly  by  hand,  is  operated  by  a  motor  or  a  large  magnet  which 
is  controlled  by  a  small,  low-potential  hand  switch.  Current  from 
the  exciter  dynamo  is  generally  used  to  work  the  motor  or  magnet 
moving  the  switch. 

These  switches  may  be  made  to  open  automatically  with  ex- 
cessive current  flow,  by  means  of  a  controlling  magnet  to  actuate 
the  switch  that  sets  in  motion  the  operating  magnet  or  motor,  the 
magnet  being  set  to  move  when  the  line  current  exceeds  a  certain 
predetermined  value.  When  so  arranged,  they  serve  the  double 
purpose  of  automatic  circuit  breakers  and  hand  switches. 

When  the  potential  exceeds  10,000  volts  and  the  amount  of 
energy  transmitted  over  each  switch  is  350  K.W.  or  more,  it  is 
advisable  to  place  each  pair  of  contacts  in  a  separate  fireproof 

141 


142       DEVELOPMENT   AND   DISTRIBUTION  OF   WATER   POWER 

chamber;  that  is  to  say,  a  three-phase  switch  becomes,  in  effect, 
three  single-phase  switches,  all  actuated  simultaneously  by  a  single 
mechanism  common  to  the  three.  The  high-tension  bus-bars  are 
also  enclosed  in  a  long  horizontal  fireproof  compartment  which 
runs  along  just  above  the  switch  compartments.  The  sides  of  this 
bus-bar  chamber  may  be  made  of  brick,  tile,  or  concrete.  Fig.  71 
shows  a  high-tension  switch  for  60,000  volts  with  its  three  contacting 


Front. 


Rear. 
FIG.  70.  (Oil  Chamber  Lowered.) 


parts  in  three  separate  brick  chambers.  This  switch  is  operated 
electrically  by  heavy  magnets  which  may  be  partly  seen,  their 
plungers  connecting  to  the  operating- chain  links  attached  to  the 
main  lever  arm. 

Ordinary  knife  switches  are  satisfactory  up  to  600  volts;  and 
where  the  energy  transmitted  over  each  switch  does  not  exceed  500 
K.W.,  these  may  be  used  as  main  dynamo  switches  with  low-ten- 
sion generators,  the  voltage  being  raised  by  step-up  transformers. 


SWITCHING   AND   CONTROLLING   APPARATUS  143 

These  also  are  used  for  the  exciter  dynamos  and  the  generator 
fields. 

The  exciter  current  is  usually  of  low  voltage,  either  125  or  250 
volts,  and  the  exciter  switchboard  is  built  on  the  same  lines  and 


FIG.  71. 

principles,  as  those  which  guide  the  design  of  any  direct-current 
switchboard,  the  instruments  being  mounted  on  marble  panels 
from  i  J  to  2  inches  thick,  which  are  in  turn  supported  on  vertical 
sections  of  angle  iron,  to  which  the  slabs  are  bolted.  Felt  or  rubber 
washers  about  one-eighth  inch  thick  should  be  interposed  between  the 


144       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER    POWER 

iron  and  the  marble.  Adjacent  panels  are  joined  together  by  bolt- 
ing the  adjoining  webs  of  two  separate  supporting  angle  bars  to- 
gether by  | -inch  bolts,  spaced  18  to  22  inches  apart  along  the 
length  of  the  angle  sections.  Fig.  72  is  a  plan  view  showing  a  por- 
tion of  two  adjoining  marble  slabs  each  bolted  to  its  supporting 
channel  bars,  the  latter  being  bolted  together.  An  angle  section 

Bolts.brass  cone-head  nuts 

"Marble 


FIG.  72. 

2  X  2\  inches  is  a  good  size  to  use,  the  narrow  web  being  bolted 
to  the  marble. 

It  is  customary  to  install  a  separate  panel  for  each  dynamo. 
The  exciter  panels  are  usually  placed  at  one  end  of  the  board,  and 
the  generator  panels  at  the  other  end.  A  totalizing  panel  is  gener- 
ally put  in  the  middle  of  the  exciter  panels  on  which  are  mounted 
instruments  to  show  the  total  output  of  all  the  exciters  working  to- 
gether, while  a  totalizing  panel  for  the  purpose  of  registering  the 
total  output  of  the  generators  is  put  in  the  middle  of  the  generator 
panels. 

There  have  been  a  number  of  methods  suggested  for  switch- 
board and  switching  connections,  some  of  which  are  highly  com- 
plicated; and  the  multiplicity  of  connections  and  the  numerous 
switches  are  more  liable  to  prove  sources  of  trouble  than  to  be 
of  much  assistance.  Furthermore,  high-tension  switches  are  ex- 
pensive and,  unless  carefully  worked  out,  the  switchboard  may  be 
a  source  of  great  and  unnecessary  expense.  Fig.  73  shows  an 
arrangement  which  the  author  considers  amply  complete  and 
flexible.  Gv  G2,  and  G3  are  three-phase  generators  excited  by  fields 
Fv  F2,  F3.  The  generators  connect  through  the  generator  switches 


SWITCHING   AND   CONTROLLING   APPARATUS 


145 


* 


QfiMb — I 

I    30 

I 


FIG.  73. 


10 


146       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

to  a  set  of  three-phase,  low-tension  bus-bars.  Tv  T^  T3,  T±  are 
step-up  transformers  connected  in  mesh  as  shown,  and  any  trans- 
former may  be  joined  to  the  low-tension  bus-bars  by  means  of  the 
low-tension  transformer  switches  which  connect  to  the  transform- 
er primaries.  These  generator  and  transformer  switches  may 
be  ordinary  knife  switches  if  the  voltage  of  the  generators  does 
not  exceed  600  volts  and  the  K.W.  capacity  is  not  above  500. 
It  is  well,  however,  to  use  automatic  circuit  breakers,  which  may 
be  tripped  by  hand,  for  the  generator  switches,  and  these  will  dis- 
connect in  case  of  overload  or  can  be  operated  manually  when 
desired. 

A  set  of  high-tension  bus-bars  has  a  series  of  high-tension 
switches  connecting  them  to  the  step-up  transformer  secondaries, 
and  the  outgoing  transmission  lines  are  joined  to  the  high-tension 
bus-bars  by  high-tension  switches  similar  to  those  connecting  the 
transformer  secondaries  to  the  high-tension  bus-bars.  The  trans- 
mission line  switches  should  be  provided  with  automatic  tripping 
coils  which  will  cause  them  to  open  if  the  current  should  exceed  a 
predetermined  amount. 

E1  and  E2  are  exciter  dynamos  which  connect  by  means  of 
ordinary  knife  switches  to  the  exciter  bus-bars.  The  generator 
fields  also  connect  to  the  exciter  bus-bars  each  through  its  own 
field  switch  as  shown,  the  current  passing  through  the  generator 
field  rheostats  Hlt  H2  and  H3.  By  means  of  rheostats  Rt  and  R2 
the  voltage  of  the  exciters  may  be  adjusted.  These  machines  may 
be  run  in  parallel  or  either  one,  singly,  can  be  used  to  supply  current 
to  the  exciter  bus-bars.  The  field  of  any  generator  may  be  switched 
onto  or  off  from  the  bus-bars,  and  each  generator  field  may  be  in- 
dividually adjusted  by  means  of  the  rheostat  in  its  circuit.  Any 
of  the  main  generators  may  be  switched  on  or  off  the  low-tension 
bus-bars,  any  transformer  may  be  cut  out  of  service,  and  either  of 
the  transmission  lines  or  both  may  be  disconnected. 

This  diagram  does  not  indicate  any  instrument  connections 
except  that  of  the  synchroscope.  As  shown,  this  is  connected  to 
the  generator  bus-bars  by  means  of  a  small  switch  on  one  side. 


SWITCHING   AND   CONTROLLING   APPARATUS  147 

Its  other  side  connects  to  several  small  switches — three  in  this 
case.  By  plugging  in  the  switch  to  the  bus-bars  and  any  one 
of  the  switches  connected  to  the  generator  terminals,  the  relative 
frequencies  of  the  bus-bar  and  the  generator  to  which  the  instru- 
ment is  connected  are  indicated.  This  device  is  for  the  purpose 
of  showing  whether  the  frequency  of  a  generator,  which  is  not 
connected  to  the  bus-bars,  is  greater  or  less  than  that  of  the  bus- 
bars, so  that  the  speed  of  the  disconnected  generator  may  be  raised 
or  lowered  until  the  frequencies  are  the  same;  and  when  this  con- 
dition is  reached,  the  pointer  comes  to  rest  in  its  middle  position 
and  thereby  indicates  that  the  synchronized  generator  is  ready  to 
be  connected  to  the  bus-bars,  it  being  assumed  that  the  voltage  has 
been  previously  adjusted  to  its  proper  value. 

Voltmeters  should  be  installed  so  that  the  following  indications 
may  be  taken: 

1.  Voltage  of  each  generator. 

2.  Voltage  of  low- tension  bus-bars. 

3.  Voltage  of  high-tension  bus-bars. 

Up  to  600  volts  voltmeters  are  connected  directly  to  the  circuit 
to  be  measured.     Above  that,  however,  a  transformer  is  connected 


FIG.  74. 

to  the  circuit,  and  the  voltmeter  is  connected  to  the  secondary  side 
of  the  transformer.  Fig.  74  shows  a  three-phase  line  with  the 
primaries  of  three  small  transformers  connected  across  the  three 


148       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

phases.  The  secondaries  leave  the  three  small  switches  which 
latter  connect  to  a  pair  of  wires  leading  to  the  voltmeter.  By 
throwing  in  any  switch  a  single  voltmeter  is  made  to  indicate  the 
voltage  of  each  of  the  three  phases.  Where  three-phase  systems 
are  balanced — that  is,  equal  current  passing  over  each  of  the  three 
wires — it  is  necessary  only  to  take  the  voltage  of  one  of  the  phases, 
as  the  voltages  of  all  the  phases  will  all  be  equal.  This  is  the 
condition  existing  in  nearly  all  transmission  systems;  and  in 
them  only  one  transformer  with  its  secondary  connected  to  the 
voltmeter  is  required. 

Ammeters  on  high-tension  circuits  are  also  connected  to  trans- 


FIG.  75. 

formers  in  which  the  primary  consists  of  one  or  two  turns  in  series 
with  the  main  current.  The  secondary  consists  of  a  number  of 
turns,  its  terminals  being  connected  to  the  ammeter.  Obviously, 
the  volts  generated  in  the  secondary  will  be  proportional  to  the 
current  in  the  main  line  passing  through  the  primary.  The  in- 
strument itself  is  in  reality  a  voltmeter;  but  the  movements  of  its 
needle  being  proportional  to  the  current  passing  in  the  main  line, 
the  markings  of  its  dial  are  in  amperes.  Fig.  75  shows  the  con- 
nections. 

Wattmeters  record  the  quantity  of  electrical  energy  generated; 


SWITCHING   AND   CONTROLLING   APPARATUS  149 

and  the  usual  type  of  integrating  instrument  makes,  a  continuous 
record  of  total  energy  delivered  over  a  certain  period  of  time. 
These  have  two  windings,  one  a  shunt,  the  other  a  series  winding; 
and  therefore,  potential  and  series  transformers  both  are  required 
for  them. 

Circuit  breakers  which  work  on  high-tension  lines  must  take 
current  for  the  tripping  coils  from  series  transformers.  It  is  cus- 
tomary, where  ammeters,  voltmeters,  and  wattmeters  are  to  reg- 
ister on  the  same  circuit,  to  put  in  one  potential  and  one  series 
transformer,  each  large  enough  to  provide  current  for  its  instru- 
ment and  the  wattmeter  also;  and  if  a  circuit  breaker  operate  on 
the  line,  the  series  transformer  is  large  enough  to  supply  current  to 
its  tripping  coil,  in  addition. 

Synchroscopes  on  high-tension  circuits  are  connected  to  the 
secondaries  of  potential  transformers  instead  of  directly  to  the 
line  as  shown  in  Fig.  73. 

Other  alternating-current  instruments  are,  power  factor  meters 
and  frequency  meters.  The  former  are  not  necessary  except  under 
certain  special  conditions,  the  second  only  a  convenience  and  in  no 
wise  essential. 

Ground  detectors  are  necessary  in  every  plant.  These  indi- 
cate the  existence  of  a  contact  between  the  earth  and  any  one  of 
the  lines.  The  type  of  detector  now  used  is  electrostatic,  in  which 
no  current  passes  through  it.  The  connection  is  made  either  direct 
to  the  instrument  or  to  the  terminals  of  a  condenser,  the  connec- 
tions in  the  former  case  being  as  indicated  in  Fig.  76.  When 
connected  directly  to  earth  a  fuse  or  graphite  resistance  must  al- 
ways be  placed  in  the  ground  connection  so  that  in  case  of  the 
vanes  becoming  bent  so  that  they  approach  each  other  and  an  arc 
should  leap  across,  the  current  flow  would  melt  the  fuse  and  pro- 
tect the  device. 

A  better  way  of  installing  these  instruments  is  to  use  small  con- 
densers which  are  supplied  for  the  purpose.  No  matter  whether 
the  vanes  are  in  contact  or  not,  the  current  flow  is  so  limited  that 
neither  the  condensers  nor  the  instrument  can  be  injured. 


150       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

The  relative  value  of  circuit  breakers  and  fuses  is  a  subject 
still  under  discussion,  and  each  case  must  be  separately  considered. 
Fuses,  when  properly  made,  can  be  used  successfully  under  po- 
tentials up  to  6,000  volts  where  the  power  does  not  exceed  100  K.W. 
Such  fuses  are  from  12  to  18  inches  in  length  and  are  surrounded 
by  porcelain  tubes,  with  sand  packed  in  the  tube  around  the  fuse. 


Ground 

FIG.  76. 

With  lower  potentials,  as  much  as  200  K.W.  may  be  interrupted 
by  fuses.  In  plants  having  units  larger  than  this,  automatic  cir- 
cuit breakers  should  be  used  and  made  to  serve  at  the  same  time 
as  switches. 

In  a  properly  designed  switchboard  there  will  be  no  parts  on 
it  carrying  high  potentials.  The  high-pressure  switches  and  bus- 
bars will  be  in  their  fireproof  compartment,  with  operating  handles 
only  on  the  face  of  the  board — usually  coming  through  the  marble 
from  the  rear — or  simply  small,  low-potential  knife  switches  to 
actuate  the  operating  magnets  or  motors  which  move  the  high-poten- 
tial switches.  All  instrument  transformers  are  mounted  either  on 
the  wall  in  the  rear  of  the  switchboard  or  on  the  horizontal  iron 
braces  running  from  the  switchboard  to  the  wall,  only  the  low- 


SWITCHING   AND   CONTROLLING   APPARATUS  151 

tension  wires  from  their  secondaries  going  to  the  instruments  on 
the  board. 

The  direct-current  panels  for  the  exciter  have  no  special  in- 
struments on  them  other  than  standard  voltmeters,  amperemeters, 
and  knife  switches,  with  the  single  exception  of  the  field  switches 
to  the  main  generator  fields.  These  are  ordinary  knife  switches 
each  having  a  pair  of  auxiliary  contact  clips  which  the  switch 
blades  do  not  touch  when  the  switch  is  closed.  In  opening  it, 
however,  the  blades  touch  these  clips  just  before  leaving  the  clips 
connected  to  the  exciter  bus-bars.  The  auxiliary  clips  are  joined 
together  by  a  resistance.  At  the  instant  when  the  switch  blades 
are  on  the  point  of  leaving  the  bus-bar  clips  and  are  making  con- 
tact with  the  auxiliary  clips,  the  resistance  is  connected  in  par- 
allel with  the  generator  field.  A  further  movement  of  the  switch 
handle  disconnects  the  blades  from  the  bus-bar  clips,  but  leaves 
them  still  in  contact  with  the  auxiliary  clips,  and  the  resistance  be- 
tween these  latter  provides  a  path  for  the  inductive  discharge  of  the 
generator  fields.  Without  such  an  arrangement,  instantaneous 
potentials  are  set  up  on  opening  the  field  circuit  which  may  be  great 
enough  to  cause  break-down  of  the  insulation. 

In  designing  the  board,  allow  not  less  than  two  inches  between 
bare  metallic  parts  of  opposite  potential  for  i25-volt  boards  and 
2j  inches  for  2  50- volt  boards.  Keep  at  least  2  inches  away  from 
the  angle-iron  supports  for  the  slabs.  Current  densities  per  square 
inch  should  be  1,000  amperes  in  bus-bars,  750  to  800  amperes  in 
the  switch  blades  and  clips,  100  to  125  amperes  between  surfaces 
bolted  together,  and  50  to  55  amperes  between  switch  blades  and 
clips. 


APPENDIX 


COMPUTATION  OF  PRESSURES  SET  UP  IN  LONG  PIPES  WITH 
CHANGE  IN  GATE  OPENING 


Abstract  from  a  paper  presented  April  9,  1906,  before  the  Ameri- 
can Institute  of  Electrical  Engineers  on 

A  NEW  METHOD  OF  TURBINE  CONTROL. 

BY  LAMAR  LYNDON. 

IN  the  case  of  a  turbine  fed  by  a  long,  closed  pipe,  it  is  evi- 
dent that  any  change  in  the  gate  opening  must  be  accompanied 
by  a  change  in  the  velocity  of  the  column  of  water,  and  since 
this  column  has  weight,  velocity,  and  is  practically  incompressible, 
kinetic  energy,  proportional  to  its  mass  and  the  square  of  the 
velocity,  is  stored  in  the  moving  water,  and  any  change  in  its  ve- 
locity must  be  accompanied  by  a  corresponding  change  in  its 
energy,  which  can  only  take  place  by  change  in  the  internal 
pressure  in  the  pipe. 

Starting  with  the  formula,  the  basis  of  mechanics, 

F  =  M  A,  in  which 

F  =  force  or  pressure  in  pounds; 

M  =  mass = weight  in  pounds  --T-  32.2; 

A  =  acceleration  in  feet  per  second; 

the  change  in  pressures  for  changes  in  gate  opening  can  be  de- 
duced. 

Let  S  =  area  of  pipe  in  square  feet. 
L  =  length  of  pipe  in  feet. 
W  =  weight  of  a  cubic  foot  of  water  =  62. 5  Ib. 
152 


APPENDIX  153 

Then  S  L  W  =  total  weight  of  water  in  the  pipe  at  any  time, 

S  LW 

and  its  mass  =  —      —  •  (i) 

32.2 

If  Cl  =  velocity  in  feet  per  second  with  a  given  gate  opening  ; 
C2  =  velocity  with  a  reduced  gate  opening; 
r=time  of  change  in  seconds, 
then  P,  the  pressure  set  up  will  be, 


32.2  T 

which  is  the  total  pressure  to  retard  the  mass  of  water. 
If  p  =  pressure  in  pounds  per  square  inch, 
P          SLW 


=  = 

P      5Xi44    5Xi44     32-2  T'      74-3  T 


this  being  the  formula  for  excess  pressure  above  that  due  to  the 
head  when  the  gate  opening  is  reduced,  or  the  reduction  in  press- 
ure to  be  subtracted  from  the  head  at  the  time  when  the  gate 
opening  is  increased.  It  is  to  be  noted  that  the  pressures  per  square 
inch  are  independent  of  the  diameters  of  the  pipes. 

As  an  example,  take  a  pipe  1,000  ft.  long;  head  at  the  tur- 
bine 90  ft.;  velocity  of  water  in  the  pipe  6  ft.  per  second  at  full 
gate.  Reduce  this  opening  to  70  per  cent,  gate  in  three-fourths  of 
a  second.  The  reduced  velocity  of  the  water  is  70  per  cent,  of  6  = 
4.2  ft.  per  second. 

1,000(6-4.2.) 

74.3X0.75 
The  head  on  the  turbine  is  90  X  0.434  =  39  Ibs.  normal.     Percent- 

32.3 

age  change  in  the  pressure  is  --  =83  per  cent. 

39 

If  the  gate  were  moved  from  70  percent,  to  100  per  cent,  opening 
as  above,  the  net  head  acting  for  the  short  time  of  gate  movement 
would  be  39—32.3  =  6.7  lb.,  or  about  17  per  cent,  of  the  normal 
head. 

When  the  gate  is  completely  closed,  the  phenomena  are  very 
different,  as  are  the  laws  which  govern  them.  These  will  now 
be  investigated. 


154       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

"If  the  gate  were  closed  instantaneously,  the  excess  pressure 
set  up  would  be  infinite. if  it  were  not  for  the  ductility  of  the  con- 
ducting pipes  and  the  elasticity  of  the  water  itself.  Because  of 
these  effects,  however,  the  pressures  produced  by  Instantaneous 
closing  of  the  gate  are  not  infinite,  but,  from  a  theoretical  view- 
point, small,  though  exceedingly  great  when  considered  as  hydrau- 
lic effects,  to  be  taken  care  of  in  practice. 

For  increase  of  pressure  when  the  valve  is   closed   instanta- 
neously the  formula  is 

*=,(*/ 


g(tE'+2RE)< 

in  which 

p  =  increase  in  pressure  per  square  inch; 
c  =  initial  velocity  in  feet  per  second ; 

a)  =  weight  of  a  prism  of  water  i  ft.  long  and  i  sq.  in.  in  cross- 
section  =0.4341 6; 

E  =  modulus  of  compressibility  of  water  =  294,000  Ibs.  per 
sq.    in.  =  294  X  io3; 

E'  =  modulus  of  elasticity  of  plate  iron  =  30,000,000  Ibs.   per 
sq.  in.  =3  X  io7; 

/  =  thickness  of  pipe  plate  in  inches; 

g  =  acceleration  due  to  gravity  =  3 2. 2; 

R  =  internal  radius  of  pipe  in  inches. 

Take,  for  example,  a  pipe  of  5  ft.  diameter,  the  thickness  of  the 
pipe  wall  being  0.25  in.,  and  the  velocity  of  the  water  in  the  pipe 
being  6  ft.  per  second.  Substituting  the  above  values  of  &>,  /,  and  R, 


whence  p  =  6  X  Vi, 182  =  206  Ibs.  per  sq.  in., — a  pressure  which 
approaches  the  rupturing  point  of  the  pipe. 

As  may  be  seen,  the  pressure  produced  by  instantaneous  clos- 
ure is  independent  of  the  length  of  the  pipe.     An  appreciable 

*Church's  "Hydraulic  Motors,"  p.  208. 


APPENDIX  155 

time,  however,  is  required  to  close  any  valve,  and  with  the  in- 
troduction of  the  time  element  the  length  of  the  pipe  also  enters 
as  a  factor  into  the  problem.  The  theory,  in  general,  of  the  phe- 
nomena which  take  place  on  instantaneous  gate  closure  is  that 
the  kinetic  energy  of  the  moving  mass  of  water  changes  to  poten- 
tial energy,  distending  the  pipe  and  compressing  the  water.  This 
compression  of  the  water  continues  for  only  an  instant,  as  imme- 
diately after  compression  it  begins  to  extend  itself;  this  act  of  ex- 
tension again  sets  up  the  pressure  and  causes  compression.  The 
cycle  is  repeated,  and  this  continues  until  the  friction  of  the  water 
in  the  pipe  and  the  molecules  against  each  other  decrease  the 
amplitude  to  nearly  zero.  The  whole  occurrence  is  an  oscillatory 
one  and  resembles  somewhat  the  phenomenon  of  "  surging"  in 
electrical  transmission  lines  carrying  alternating  currents.  The 
velocity  of  the  "wave  propagation"  is  the  same  as  the  velocity  of 
sound  in  water,  and  this  velocity  varies  with  varying  conditions  of 
thickness  of  pipe  shell,  modulus  of  material  of  shell,  and  its  inter- 
nal radius.  The  formula  for  the  velocity  of  wave  propagation  is, 


(5)* 

Formula  (4)  may  also  be  written 

in  which  v  =  velocity  of  wave  propagation  in  feet  per    second; 
W  =  weight  of  a  cubic  foot  of  water. 

V-*L 
~cW 

If  p  =  2o6  as  given  in  the  foregoing  problem, 

t 

206X144X32.2  , 

V=         6X62.5         =2.54°  ft.  per  sec. 


*  Church's  "Hydraulic  Motors,"  p.  208. 

t  Constant  144  is  to  reduce  the   cross-section  of  a  cubic  foot  of  water  to 
square  inches. 


156       DEVELOPMENT   AND   DISTRIBUTION  OF   WATER   POWER 

Assume  the  pipe  1,000  ft.  in  length.  Then  the  time  required 
for  the  wave  to  travel  from  the  gate  back  to  the  end  of  the  pipe 

and  return  to  the  gate  is—          -  =0.788  second.     This  may  be 

2,540 

termed  the  "time  constant"  of  the  pipe  for  the  velocity  of  water 
flow  of  6  ft.  per  sec.,  and  designated  by  7\  If  the  gate  be  closed 
within  the  time  of  one  complete  wave  cycle,  i.e.,  0.788  second  for 
this  case,  the  pressure  set  up  is  the  same  as  ij  the  gate  had  been  closed 
instantaneously. 

If  the  pipe  were  3,000  ft.  long,  the  time  constant  would  ob- 
viously be  three  times  the  above  or  2.364,  say  2j  seconds,  and,  in 
order  to  avoid  the  heavy  pressure  computed,  the  gate  must  not 
close  within  this  time  of  2^  seconds. 

If  a  longer  time  be  taken  to  close  the  gates,  the  pressure  set 
up  will  be  directly  proportional  to  pressure  due  to  instantaneous 
closing  in  the  inverse  ratio  of  To  to  T^  where  T  is  the  time  in 
which  the  gate  is  closed;  that  is,  p  :  p"  : :  TC  :  Tx.  Thus  if  4.5 
seconds  are  taken  to  close  the  gate,  for  conditions  as  above  and  a 
length  of  pipe  of  1,000  ft.,  the  pressure  produced  will  be  206  X 

=  36  Ibs.     For  a  3,ooo-ft.  length  of  pipe  the  pressure  will 

4-5 

2.264 
be  206  X  -     -  =  108  Ibs. 

4-5° 

These  formulas  and  facts  have  all  been  experimentally  proved 
by  Joukovsky  in  a  series  of  experiments  conducted  at  Moscow, 
Russia,  in  1897-1898,  in  pipes  up  to  24  in.  in  diameter.  They 
show  conclusively  the  necessity  for  compensating  for  the  change 
in  energy  in  the  water  column  at  the  time  of  governing,  if  the 
gates  are  to  be  moved  quickly  for  rapidly  fluctuating  loads. 


PART  III 

DESCRIPTIONS  OF  HYDRO-ELECTRIC  GENERATING 
AND  TRANSMISSION  PLANTS. 

THE  TOFWEHULT-WESTERWIK  TRANSMISSION  SYSTEM, 
SWEDEN. 

Abstract  from  "  Electrical  World  "  Sept.  28,    1907. 

AN  electrical  equipment  recently  installed  in  Sweden  for  trans- 
mitting energy  from  Tofwehult  to  Westerwik  possesses  some 
interesting  details,  which  are  outlined  below.  The  plant  con- 
sists of  a  power-house  at  Tofwehult,  a  transmission  line  thence  to 
the  town  of  Westerwik,  and  transformer  and  converter  stations 
in  that  town. 

THE  POWER-HOUSE. 

The  natural  surroundings  of  the  waterfall  at  Tofwehult  rendered 
it  especially  favorable  for  development,  because  it  is  situated  be- 
tween two  lakes,  and  the  connection  between  these,  which  forms 
the  fall,  consists  of  a  deep  cleft  with  almost  vertical  sides.  In 
consequence  the  hydraulic  work  was  very  simple  and  cheap; 
the  costs  of  the  hydraulic  work  and  the  power-house  building 
amounted  to  only  $26,000,  which,  on  the  basis  of  the  maximum 
output  of  1,300  horse-power,  including  the  reserve,  is  only  $20  per 
horse-power.  The  power-house  is  built  for  three  generating  sets, 
two  for  325  H.  P.  each,  and  one  fof  650  H.  P.  Only  the 
two  smaller  sets  are  now  installed. 

The  turbines  showed  under  test  an  efficiency  at  full  load  of 
8 1  per  cent.,  and  a  speed  variation  of  only  6  per  cent,  at  a  load 
variation  from  full  load  to  no  load.  An  interior  view  of  the 
power-house  is  shown  in  Fig.  77.  Each  of  the  generators  is  built 

'57 


158       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

for  10,000  volts  and  285  K.V.A.  The  major  insulation  of  the 
armature  coils  consists  of  several  layers  of  oiled  cloth  and  a  final 
coating  of  an  insulating  compound.  At  the  insulation  test  of  one 
of  these  coils,  the  break-down  occurred  at  45,000  volts. 

A  separate  extension  of  the  power-house  is  provided  for  the 


FIG.   77. — INTERIOR  OF  POWER-HOUSE. 

switch  gear,  as  seen  in  the  illustration  Fig.  78.  The  lightning  ar- 
resters are  placed  on  the  upper  floor  of  this  extension.  The  lower 
floor,  which  is  separated  from  the  generator  hall  by  the  switch- 
board, contains  all  other  apparatus  and  instruments  for  low 
and  high  tension.  The  high-tension  equipment  is  placed  in  a 
compartment  separated  by  iron  gratings  and  accessible  from 
both  sides. 

In  order  to  prevent  the  accumulation  of  static  electricity  on 
the  high-tension  line  a  static  protector  is  provided.  This  ap- 
paratus consists  of  six  vertical  glass  pipes,  two  for  each  phase, 
(Fig.  78),  through  which  water  flows  continuously.  The  upper 
connection  between  the  two  pipes  of  each  phase  consists  of  an  iron 
faucet  which  is  connected  to  the  corresponding  bus-bar.  The  iron 
pipes,  through  which  the  water  is  carried  to  and  from  the  ap- 
paratus and  which  are  connected  to  the  lower  ends  of  the  glass 


TOFWEHULT    WESTERWIK    PLANT 


159 


pipes,  arc  grounded.  The  water  being  very  pure  and  therefore 
its  specific  resistance  being  high,  the  current  leaking  through 
the  apparatus  is  small,  amounting  to  only  0.036  amp.  per  lead; 


FIG.  78. — LIGHTNING  ARRESTERS 

this  value  is  probably  rather  too  small  to  secure  a  good  efficiency 
of  the  device. 

THE  HIGH-TENSION  LINE. 

About  half  way  between  Tofwehult  and  Westerwik  a  deep 
bay  of  the  Baltic  cuts  into  the  land.  If  the  transmission  line 
had  been  erected  around  this  bay  the  length  would  have  been 
increased  by  3.75  miles  above  the  straight  distance  of  about  9 
miles  between  the  power-house  and  the  town.  The  increase 
could  be  avoided  by  crossing  the  bay  by  means  of  either  a  sub- 
marine cable  or  a  long  overhead  span.  In  order  to  obtain  suffi- 
cient security  against  break-downs  of  a  cable  in  the  middle  of  an 
overhead  line  of  10,000  volts  it  would  have  been  necessary  to  in- 
stall special  protection  devices  and  to  lay  two  cables.  Even 
if  these  provisions  had  been  made,  the  crossing  by  cable  would  not 


l6o       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

only  entail  a  lower  degree  of  working  security,  but  would  also 
cause  higher  running  costs.  Since,  not  far  from  the  straight  line 
between  the  power-house  and  the  town,  the  bay  forms  a  narrow 
strait  with  steep  shores,  it  was  decided  to  build  at  this  point  an 
overhead  span  of  sufficient  height  to  avoid  all  sails.  The  length 
of  the  span  is  735  ft.,  and  the  Height  over  the  water  is,  at  the  lowest 
point,  131  ft.  The  conductors  consist  of  steel  wire  ropes,  each  60 
sq.  mm.  in  cross-section;  they  are  supported  by  iron  masts,  each 
having  a  height  of  82  ft.,  two  on  each  side,  which  carry  insula- 
ting supports. 

A  view  of  an  insulating  support  is  given  in  Fig.  79.     It  con- 
sists of  an  oak  block,  resting  on  six  high-tension  insulators.     The 


Sheet  lead 


FIG.  79. — SADDLE  SUPPORT  FOR  LONG  WIRE  SPAN. 

insulators  are  cemented  to  the  oak  block,  their  iron  pins  being 
fastened  to  the  brackets  of  the  mast.  The  oak  block  is  protected 
against  moisture  by  a  coating  of  sheet  zinc.  In  order  to  prevent 
the  pull  of  the  wire  ropes  from  acting  on  the  masts,  a  rolling  de- 


TOFWEHULT    WESTERWIK    PLANT 


161 


vice  is  provided.  The  rolling  device  consists  of  a  cast-iron  plate 
resting  on  the  oak  block,  four  cast-iron  rolls,  and  a  cast-iron  piece 
which  rests  on  these  rolls  and  to  which  the  wire  ropes  are  fastened 
by  screws.  The  terminals  of  the  wrire  ropes  are  anchored  to  the 
rock.  Thus  they  act  as  a  guy  to  the  casting  to  which  the  wire  rope 
is  fastened,  and  prevent  it  from  rolling  out  of  the  cast-iron  plate. 
Slipping  to  the  side  is  prevented  by  flanges  on  the  rolls.  Four 
wire  ropes  are  mounted  in  this  way,  one  of  which  serves  as  reserve. 
As  stated  the  cross-section  of  each  rope  is  60  sq.  mm.  Each 
wire  rope  has,  therefore,  the  same  conductivity  as  a  copper 
wire  about  7  sq.  mm.  in  cross-section.  At  30°  C.  the  strain  in 
the  span  part  of  the  rope  is  1,300  Ibs.,  and  in  the  guy  part  i,65olbs. 
Thus  the  maximum  stress  equals  17,800  Ibs.  per  sq.  in.,  corre- 
sponding to  a  safety  factor  of  5.  The  sag  of  the  rope  at  30°  C. 
equals  29.5  ft.  In  spite  of  this  sag  a  contact  between  the  ropes 


FIG.  80. — METHOD  OF  ANCHORING  WIRE  CABLE  SPAN. 

is  impossible,  since  they  are  mounted  at  different  heights,  and  the 
horizontal  distance  of  about  6.5  ft.  is  ample.  Moreover,  it  has 
been  proved  that  even  in  a  strong  wind  the  wires  do  not  swing; 
all  of  the  ropes  are  deviated  to  the  same  constant  angle  from 
the  vertical  plane  whereby  the  distance  between  the  ropes  is 
not  changed. 

As  the  wire  ropes  are  anchored  to  the  rock  it  is  necessary  to 


1 62          DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

put  special-strain  insulators  into  the  guy  part  of  the  ropes.  The 
strain  insulator  which  is  shown  in  Fig.  80  must  withstand  a  me- 
chanical force  of  1,650  pounds  and  at  the  same  time  secure  a 
good  insulation.  The  insulators  are  coupled  in  series  by  twos; 
therefore,  at  the  regular  working  conditions  each  insulator  is  sub- 
jected to  a  voltage  of  3,000.  Still,  in  order  to  get  a  high  degree 
of  security,  each  insulator  was  designed  for  20,000  volts.  The 
insulator  is  covered  on  the  top  and  sides  by  a  cap  of  sheet  zinc 
whereby  it  is  perfectly  protected  against  moisture.  The  dry  insu- 
lator in  actual  tests  withstood  a  tension  of  25,000  volts.  As  to 
the  mechanical  strength  a  lining  of  sheet  lead  between  the  iron 
and  the  porcelain  effects  an  equal  distribution  of  the  mechanical 
pressure  upon  the  latter;  and  since  porcelain  possesses  a  great 
strength  against  pressure  it  was  not  difficult  to  make  the  span  in- 
sulators sufficiently  strong  mechanically. 

A  telephone  circuit  is  erected  on  the  high-tension  line  poles. 
For  this  line  common  telephone  insulators  are  used;  the  tele- 
phone lines  are  transposed  at  every  fifth  pole.  The  high-tension 
line  is  transposed  one  turn  at  every  1,000  ft.  In  telephoning  over 
this  line  a  humming  sound  is  heard.  The  noise  is  not  so  loud  as 
to  disturb  the  conversation.  It  is  probably  partially  caused  by  the 
grounding  of  the  neutral  point  at  both  the  transformer  station 
and  (through  the  static  protectors)  in  the  power-house. 

TRANSFORMER  AND   CONVERTER   STATIONS   AND   DISTRIBUTING 

CABLE. 

In  the  main  transformer  station  at  Westerwik  the  current 
is  transformed  to  500  volts  three-phase  and  3,000  volts,  three- 
phase.  The  former  voltage  is  used  for  distribution  within  an 
industrial  district  in  the  neighborhood  of  the  transformer  sta- 
tion; the  latter  is  used  for  transmission  to  the  converter  station 
which  is  built  close  to  the  old  city  plant.  The  converter  station 
is  arranged  for  four  motor-generator  sets;  two  of  those  are  in- 
stalled at  present.  The  direct  E.M.F.  is  2  X  no  volts,  but  every- 


TOFWEHULT    WESTERWIK    PLANT  163 

thing  is  so  planned  that  later  on  an  E.M.F.  of  2  X  220  volts  can 
be  adopted  without  any  difficulty.  The  station  reserve  equipment 
includes  a  storage  battery,  while  the  steam-driven  direct-current 
generators  of  the  old  city  plant  also  constitute  a  valuable  reserve. 
Transformer  station  No.  2  supplies  energy  to  some  factories  in  its 
neighborhood  by  means  of  three-phase  current  at  500  volts. 

The  distribution  of  the  direct  current  used  in  private  lighting, 
for  small  motors,  and  for  the  street  lamps  within  the  city  is  ac- 
complished by  means  of  underground  cables.  The  street  lighting 
is  furnished  by  65  enclosed,  7 -ampere  arc  lamps.  The  lamps  are 
connected  two  in  series  across  the  2  20- volt  supply  mains. 

The  costs  given  below  refer  to  the  two  generator  sets  installed 
at  the  present  time.  The  total  cost  of  the  fully  installed  power- 
house and  equipment  for  1,300  H.P.  would  be  about  $46,000. 
Referred  to  the  entire  equipment  including  the  reserve,  namely 
880  K.W.,  the  cost  was  $52.70  per  K.W.  at  the  power-house  and 
$65.40  at  the  end  of  the  high-tension  line;  the  corresponding 
costs  per  horse-power  are  $39  and  $48,  respectively. 

The  following  list  costs  of  various  items  may  prove  of  interest: 

COST   OF  EQUIPMENT. 

Dam  and  power-house $26,200.00 

Two  325-H.P.  turbines  and   two  43-H.P.  turbines.  .  .  .     4,800.00 

Two  285-]$.. W.  and  two  30- K.W.  generators 5,200.00 

Station  wiring  and  instruments 1,900.00 


>,ioo.oo 

Nine  miles  (27  total)  of  circuit,  19.6  sq.  mm.,  includ- 
ing poles  and  right  of  way $11,000.00 

$49,100.00 


164       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

HYDRAULIC  DEVELOPMENT  AT  WEST  BUXTON,  ME. 

Abstracted  from  The  Engineering  Record  o)  July  27,  1907. 

THERE  has  been  installed  at  West  Buxton,  about  20  miles  west 
of  Portland,  Me.,  a  3,ooo-K.W.  plant  for  the  transmission  of  a  three- 
phase,  6o-cycle,  3o,ooo-volt  current  to  the  Electric  Lighting  Com- 
pany at  Portland.  It  will  be  operated  by  hydraulic  power  devel- 


FIG.  81. — DAM  AND  POWER-HOUSE. 

oped  in  the  Saco  River  and  involves  the  construction  of  a  dam  about 
300  ft.  long,  33  ft.  in. extreme  height,  and  28  ft.  in  width  at  the  base, 
a  100  X  loo-ft.  power-house,  a  40  X  ico-ft.  dynamo-house  with 
four  750-K.W.  units,  turbines  and  other  machinery  required,  a  i5o-ft. 
boom,  a  log  chute,  and  a  50  X  3oo-ft.  tail  race. 

At  the  site  the  river  has  a  width  of  350  ft.,  an  average  depth  of 
3  ft.,  and  a  velocity  of  about  6  ft.  per  sec.  at  ordinary  stages  of  the 
water.  A  4-span  highway  bridge  formerly  crossed  the  river  about 
100  ft.  below  the  present  dam  and  slightly  oblique  to  it,  a  crib  dam 


WEST  BUXTON  PLANT 


crossed  the  river  about  50  ft.  above  it  and  connected  at  the  east  end 
with  an  old  grist-mill  and  other  buildings  which  occupied  the  site 
of  the  power-house. 

The  dam  is  approximately  perpendicular  to  the  shore  line  and 


1 66       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

nas  a  standard  cross- section  with  curved  crest  and  ogee  face  down- 
stream, a  vertical  face  upstream,  and  a  depressed  footing  or  cut- 
off wall  at  both  the  up  and  downstream  longitudinal  edges  of  the 
foundation.  The  west  end  of  the  dam  makes  an  oblique  angle  with 
a  concrete  abutting  wall  which  it  intersects  and  with  which  it  is 
integral;  the  footings  of  this  wall  are  carried  down  to  rock  and  it 
has  a  maximum  height  of  10  ft.  with  a  top  width  of  3  ft.  It  ex- 
tends about  100  ft.  upstream  from  the  dam  to  intersections  with  the 
maximum  flow  lines  of  the  impounded  water  and  is  carried  up  to  a 
height  of  8  ft.  above  the  crest  of  the  dam,  thus  concentrating  all 
flow  over  the  crest  of  the  dam  and  protecting  the  bank  on  the  down- 
stream side.  The  wall  was  built  in  an  open  cut  with  i  :  i  slopes 
and  was  back-filled  on  the  shore  side,  the  river  side  being  left  un- 
filled and  excavated  near  the  dam  to  a  depth  of  3  ft.  below  the  crest. 
At  the  opposite  end  of  the  dam  a  sluice  n  ft.  wide  and  2  ft.  deep 
below  the  crest  is  built  to  afford  a  runway  chute  for  logs,  and  slopes 
rapidly  downward  to  a  point  about  10  ft.  beyond  the  lower  face 
of  the  dam  where  it  is  below  water-level.  The  sluice  is  integral 
on  the  river  side  with  the  dam  and  on  the  shore  side  with  the  outer 
wall  of  the  power-house  foundations.  Normally,  the  sluice  is 
opened,  and  the  water  discharged  through  it  somewhat  reduces  the 
depth  on  the  crest  of  the  dam,  but  provision  is  made  for  closing  it 
if  necessary  by  stop  planks  fitting  recesses  in  the  side  walls  near  the 
upper  end. 

The  power-house  foundations  are  of  concrete  up  to  a  level  7.5 
ft.  above  the  dynamo  floor,  above  which  the  structure  is  entirely 
of  brick  and  steel  except  on  the  side  toward  the  turbine  chambers, 
which  are  separated  from  the  dynamo  room  by  a  concrete  wall 
extending  8  ft.  above  the  crest.  The  floor  of  the  dynamo  room  is 
13  ft.  below  the  crest  of  the  darn ;  and  in  order  to  provide  for  a 
possible  flood  such  as  was  caused  by  an  ice  gorge  eight  years  ago, 
the  windows  and  doors  are  7  J  ft.  above  the  floor,  and  the  walls  are 
made  reasonably  tight  up  to  that  height.  Water  is  admitted  to  the 
turbine  chambers  through  five  rectangular  16  X  i6-ft.  openings 
between  the  four  longitudinal  interior  foundation  walls  which  are 


WEST  BUXTON  PLANT 


I67 


extended  about  23  ft.  beyond  the  intake  gate  to  form  piers  with 
slightly  inclined  cutwaters  and  which  rest  on  a  concrete  founda- 
tion on  the  solid  rock  22  ft.  below  the  crest  of  the  dam.  The  piers 
support  on  their  upstream 
faces  a  continuous  rein- 
forced concrete  girder  with 
an  irregular  cross-section 
about  8  ft.  deep  and  7  ft. 
wide,  having  its  lower  sur- 
face 2  ft.  below  the  crest  of 
the  dam  to  form  a  sort  of 
boom  to  intercept  any 
floating  material  and  also 
a  support  for  needles  for 
closing  any  penstock  above 
the  gates,  as  well  as  mak- 
ing foundations  for  a  fu- 
ture house  over  gates, 
hoists,  and  screens.  A  de- 
pressed walk  2\  ft.  wide 
and  3  ft.  above  the  crest  of 
the  dam  provides  a  plat- 
form from  which  it  is  easy 
to  push  the  debris  along 
the  face  of  the  boom  and 
from  which  needles  may 
be  placed.  About  7  ft.  in 
the  clear,  downstream  from 
this  girder  there  is  a  second 
thin  horizontal  girder  sup- 
ported on  the  piers  and 
extending  across  the  full 
width  of  the  power-house.  It  has  a  horizontal  and  inclined  sur- 
face forming  the  bottom  and  one  side  of  a  trough  opening  into  the 
log  chute.  The  downstream  side  of  the  trough  is  vertical  and  is 


1 68       DEVELOPMENT   AND   DISTRIBUTION  OF   WATER   POWER 

formed  by  horizontal  planks  separating  it  from  the  gates.  The  up- 
stream edge  of  the  trough  is  at  the  level  of  the  dam  crest  and  forms 
a  support  for  the  inclined  rack-bars  23  ft.  3  in.  long  and  2  in.  apart 
on  centres.  The  feet  of  these  bars  take  bearings  on  a  concrete  footing 


WEST  BUXTON  PLANT  169 

and  they  are  intermediately  supported  by  three  lines  of  equidistant 
horizontal  I-beams.  A  timber  platform  is  carried  by  transverse 
I-beams  4  ft.  above  the  top  of  the  trough  and  permits  an  attendant 
easily  to  float  the  ice  which  may  accumulate  against  the  masonry 
or  rack  over  the  edge  of  the  trough  and  thence  push  it  or  allow  the 
current  in  the  trough  to  carry  it  down  to  the  log  sluice. 

The  floor  of  the  turbine  room  is  made  with  massive  concrete 
arches  without  reinforcement  which  are  2.5  ft.  thick  at  the  crown 
and  are  carried  by  the  3 -ft.  longitudinal  interior  walls  in  the  plane 
of  the  outside  piers  above  mentioned.  The  tops  of  these  walls 
are  pitched  both  ways  from  the  centres  to  the  springing  line  so  as 
to  give  radial  surfaces  for  the  skewback  bearings.  The  footings 
of  these  walls  are  carried  down  39  ft.  below  the  crest  of  the  dam,  or 
i  ft.  below  the  level  of  the  main  excavation.  The  roof  over  the 
turbine  room  is  similar  in  construction  to  its  floor,  but  the  arches 
are  only  i  ft.  thick  at  the  crown  and  arc  pierced  over  the  centres 
of  the  turbines  with  large  circular  holes  closed  with  doors  made 
with  two  crossed  courses  of  planks.  This  floor  forms  an  open  plat- 
form between  the  front  wall  of  the  dynamo-house  and  the  gate-hoist 
foundation  which  is  a  hollow  concrete  parapet  6  ft.  wide  and  7  ft. 
high. 

The  entire  area  of  the  dynamo  room  is  commanded  by  a  travel- 
ling crane  of  34  J  ft.  span,  and  15  tons  capacity,  with  its  rails  5  ft. 
clear  of  the  lower  ends  of  the  roof  beams.  These  latter  are  20-in. 
deep,  spaced  7  ft.  8  in.  apart  on  centres  and  are  pitched  about  i  in 
36.  They  carry  a  continuous  4-in.  slab  of  concrete,  reinforced  by 
No.  10  expanded  metal  with  3-in.  meshes  which  is  covered  with 
tar  and  gravel. 

The  intakes  are  closed  by  vertical  wooden  gates  made  of  4-in. 
horizontal  planks  with  pairs  of  8  X  lo-in.  vertical  lifting  beams 
bolted,  keyed,  and  X-braced  to  them  and  provided  with  cast-iron 
racks  engaging  pinions  operated  by  hand  from  the  deck  above. 
Many  logs  are  run  down  the  river  and  are  diverted  from  the  power- 
house by  the  main  boom  which  extends  from  the  log  sluice  to  the 
river  bank  at  a  point  about  no  ft.  upstream,  thus  making  an  angle 


170       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

of  about  forty-five  degrees  with  the  face  of  the  power-house  and 
facilitating  the  movement  of  logs  and  other  drifting  material  to  the 
sluice.  It  is  a  horizontal  concrete  girder  with  a  T-shaped  cross- 
section  8  ft.  deep  and  5  ft.  wide  with  vertical  and  horizontal  webs 
respectively  2  ft.  and  i  ft.  in  thickness.  The  vertical  web  is  rein- 
forced by  19  rods  with  areas  of  i  sq.  in.  spaced  5  in.  apart,  lapped 
2  ft.  at  joints  and  located  2  in.  from  the  downstream  face  of  the 
beam.  The  horizontal  web  is  reinforced  by  six  bars  each  with  an 
area  of  .62  sq.  in.  spaced  6  in.  apart,  lapped  13  in.  at  joints  and 
located  2  in.  above  its  lower  surface  and  forms  a  walk.  The  booms 
are  supported  on  concrete  piers  4  ft.  thick,  with  both  sides  bat- 
tered 4:1  and  nearly  23  ft.  apart  on  centres.  The  girder  is  made 
continuous  with  three-panel  lengths  and  butt  joints  for  expansion 
on  the  centre  line  of  the  centre  pier,  the  river  abutment,  and  the 
last  pier  at  the  shore  side. 

The  existing  dam,  over  100  years  old,  was  made  with  cribs  filled 
with  stone,  and,  although  in  excellent  preservation,  was  so  leaky  that 
all  the  silt  and  sediment  had  washed  through  it  from  the  pond  above. 
It  was  made  tight  with  sand  bags  put  in  place  by  divers,  and  the 
crest  was  raised  5  ft.  with  flash  boards  supported  on  triangular 
wooden  frames,  the  west  end  being  torn  out  to  take  the  flow.  A 
low  earth  dam  or  dike,  sheeted  on  the  lower  side,  was  built  nearly 
across  the  river  below  the  site  of  the  new  dam,  and  the  river  diverted 
to  a  channel  near  the  west  bank  by  a  cofferdam  200  ft.  long  on  the 
east  side  of  the  channel  parallel  to  the  shore  line  and  connecting 
the  old  dam  and  the  dike  below.  It  was  made  with  timber  cribs 
15  ft.  high,  12  ft.  long,  and  16  ft.  wide  floated  to  place,  filled  with 
sand,  and  sheeted  with  3-in.  ton gue-and -groove  vertical  planks. 
The  area  between  the  dams  was  drained  and  kept  dry  with  a  single 
pulsometer  and  a  6-in.  steam  pump.  The  surface  of  the  granite 
rock  was  found  smooth  and  regular,  but,  on  account  of  the  deep 
seams  it  contained,  was  excavated  with  steam  drills  and  dynamite 
to  a  depth  of  4  to  8  ft.  for  the  footings  of  the  new  dam. 

A  concrete  platform  33  ft.  above  the  river  bottom  was  built 
on  falsework  trestle  bents  at  the  level  of  the  highway  on  the  east 


172       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

bank  of  the  river.  Stone  from  the  excavation  was  broken  and 
stored  in  a  i,ooo-yd.  pile  on  the  opposite  side  of  the  road  from  the 
platform,  where  sand  and  gravel  were  also  delivered  by  wagons. 
Cement  was  stored  in  adjacent  buildings,  and  all  of  the  material  was 
delivered  by  wheel-barrows  to  the  centre  of  the  platform,  where 
they  were  measured  and  chuted  through  trap-doors  to  two  mixers 
under  the  platform  which  delivered  the  concrete  to  i-yd.  bottom- 
dump  steel  buckets  on  flat  cars  on  a  2 -ft.  track  on  a  service  platform 
about  400  ft.  long  and  16  ft.  above  the  bottom  of  the  river.  The 
concrete  was  delivered  to  six  guyed  derricks  with  5-ton,  6o-ft. 
booms  which  commanded  the  entire  length  of  the  dam  and  handled 
the  forms  and  all  materials.  They  were  operated  by  double  drum 
engines  and  handled  a  maximum  of  about  200  yds.  of  concrete  daily. 

The  concreting  was  carried  on  without  interruption  during 
the  coldest  weather  and  when  the  temperature  was  as  low  as  minus 
47°.  The  only  precautions  taken  were  to  mix  the  concrete  with 
hot  water  and  to  soak  the  broken  stone  in  a  hot-water  tank  large 
enough  for  two  i-yd.  skips  and  heated  by  exhaust  steam  from  the 
steam-engine  and  live  steam  from  the  hoisting-engine  boilers. 
Although  the  sand  was  used  cold,  the  concrete  was  so  hot  when 
first  mixed  that  sometimes  the  men  could  scarcely  walk  in  it  with 
rubber  boots.  It  was  covered  at  night  with  tarpaulins  and  in  the 
morning  was  found  still  moist  and  unfrozen. 

The  dam  was  made  in  alternate  sections  40  ft.  long,  bonded 
together  with  four  vertical  triangular  12  X  i2-in.  keys  18  in.  apart  in 
the  clear.  They  terminated  2  ft.  below  the  upper  surface  of  the  dam. 

Derrick  stones  up  to  i  yd.  in  volume  were  bedded  in  the  con- 
crete and  formed  about  30  per  cent,  of  its  mass.  Care  was  taken 
in  filling  the  moulds  to  complete  a  horizontal  course  over  the  whole 
surface  each  day,  a  requirement  which  necessitated  the  men  some- 
times working  from  12  to  14  hours;  corresponding  heights  of  from 
3  to  8  ft.  a  day  were  secured  according  to  whether  the  work  was  at 
the  base  or  the  top  of  the  dam.  Successive  courses  were  bonded 
together  by  large  stones  embedded  in  the  surface  so  as  to  project 
half-way  above  the  top  of  the  lower  course  and  tooth  with  the  upper 


WEST    BUXTON   PLANT 


173 


course.  The  forms  were  built  of  2 -in.  square-edged  dressed  pine 
planks  and  were  not  interchangeable,  being  knocked  down  as  each 
one  was  stripped  and  rebuilt  for  the  next. 

The  main  generators  are  of  the  revolving-field  type  and  are 


FIG.  86. — SWITCHBOARD. 


174       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

designed  to  carry  an  overload  of  25  per  cent  for  two  hours  without 
excessive  overheating.  They  have  a  full-load  efficiency  of  94  per 
cent,  and  an  efficiency  of  91  per  cent,  at  half  load. 

The  switchboard  and  transformers,  in  two  banks  of  three  each, 
are  arranged  in  a  row  opposite  the  generating  machinery.  The 
transformers  are  rated  at  500  K.W.,  and  are  oil-insulated  and 
water-cooled.  The  cooling  water  is  circulated  through  a  coil  in 
the  upper  part  of  the  transformer  tank  over  the  core  and  surround- 
ing the  ends  of  the  windings.  The  water  is  taken  from  the  fore- 
bay,  near  the  exciter  turbines,  and  carried  beneath  the  floor  in  two 
3-in.«pipes,  which  are  connected  by  a  third  3-in.  pipe  running  cross- 
wise under  the  transformers.  This  cross  pipe  is  connected  with 
another  lateral  pipe  lying  close  to  the  transformers,  by  risers  in 
which  are  placed  suitable  screens.  One-inch  pipes  lead  directly 
to  the  respective  transformers  from  the  secondary  lateral  pipe. 
A  glass  is  provided  in  the  water  circuit  of  each  transformer  so  that 
the  circulation  is  always  under  observation.  From  the  transform- 
ers the  discharge  pipes  lead  downward  into  the  tail-race. 

The  switchboard  and  apparatus  are  designed  for  a  current 
capacity  commensurate  with  the  2 2,000- volt  transmission  press- 
ure, and  automatically  operated  oil  switches  are  used  on  the  out- 
going lines.  There  are  nine  principal  panels  as  follows :  One  ex- 
citer panel,  one  regulator  panel,  four  three-phase  generator  panels, 
one  transformer  panel,  and  two  outgoing  line  panels. 

The  design  of  the  West  Buxton  plant,  and  in  particular  the 
transmission  system,  is  based  on  the  purpose  of  ultimately  unit- 
ing the  service  with  that  of  the  Great  Falls  water-power  plant 
at  a  main  transformer  station  in  Portland.  The  transmission 
lines  from  the  Great  Falls  plant  are  to  be  carried  direct  to  the 
new  station.  This  will  permit  the  abandonment  of  several  sub- 
stations and  auxiliary  plants.  The  high-tension  current  from  both 
West  Buxton  and  Great  Falls  will  be  reduced  to  a  uniform  pressure 
of  2,300  volts  for  transmission  to  the  Consolidated  Electric  Light 
Company's  plant.  There,  motor-generator  sets  are  placed  for 
converting  the  united  output  to  direct  current  at  250  volts,  which 


WEST   BUXTON   PLANT 


175 


is  distributed  by  a  three-wire  system  throughout  the  business  sec- 
tion of  the  city.  At  present  there  are  installed  at  the  main  trans- 
former station  mentioned  six  5OO-K.W.,  2 2, 000/2, 300- volt  self- 
cooled  units,  with  provision  for  further  transformer  equipment  to 
handle  the  Great  Falls  output. 

The  transmission  line  from  the  West  Buxton  plant  to  Portland 
consists  of  two  three-phase  circuits  of  No.  2  wire,  a  metallic  tele- 


FIG.  87. — TRANSMISSION  LINE. 

phone  circuit  of  No.  12  copper  wire,  and  a  ground  circuit  of  No. 
12  phono-electric  wire.  The  main-line  insulators  are  triple  petti- 
coated  glazed  porcelain,  and  are  mounted  on  hard  maple  pins. 
The  circuits  are  carried  one  on  either  side  of  the  pole  on  two  cross- 
arms,  and  the  triangles  are  inverted.  The  wires  are  placed  36 
ins.  apart.  The  telephone  wires  are  carried  on  brackets  below  the 
lower  arm,  while  the  ground  wire  is  run  over  the  tops  of  the  poles 


176       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

and  grounded  at  every  sixth  pole  through  a  No.  4  B.  &  S.  copper 
wire,  connected  by  a  brass  screw-plug  with  a  galvanized-iron  pipe 
driven  6  ft.  in  the  ground.  The  cross-arms  are  of  long-leaf  yellow 
pine,  and  are  doubled  at  points  of  curvature  on  the  line.  The  poles 
are  " butt-cut"  chestnut  and  vary  from  35  ft.  to  60  ft.  in  length, 
having  a  minimum  diameter  at  the  top  of  8  ins.  The  spacing  is 
100  ft.  on  tangents. 


THE  HYDRAULIC  POWER  DEVELOPMENT  OF  THE 
ANIMAS  POWER  AND  WATER  COMPANY. 

Abstracted  from   The  Engineering  Record  of  April   14,    1906. 

THE  Animas  Power  and  Water  Company  was  incorporated  in 
Colorado  for  the  purpose  of  building  irrigation  canals,  reservoirs, 
and  developing  water  power.  The  first  work  of  importance  under- 
taken by  the  company  was  the  building  of  the  Animas  power  plant, 
which  is  located  on  the  Animas  River  and  a  branch  of  the  Den- 
ver &  Rio  Grande  Railroad,  about  half  way  between  Durango  and 
Silverton,  just  above  the  Animas  Canyon. 

The  power-house  is  a  1 08  X  64  foot  brick  and  concrete  building 
with  a  roof  of  steel  and  concrete,  making  it  as  nearly  fireproof  as 
possible.  The  building  was  erected  to  accommodate  four  units, 
only  two  of  which  are  at  present  installed.  The  others  are  to  be 
put  in  later.  The  leading  features  of  the  building  are  shown  in 
the  cross-section  and  photograph  (see  Figs.  91  and  92).  The  com- 
pany has  at  present  contracts  for  more  than  4,000  H.P. 

The  power  is  derived  from  water  taken  from  Cascade  Creek 
and  the  watershed  tributary  to  the  large  reservoir.  Cascade  Creek 
has  a  flow  of  3,720  cubic  feet  per  minute  and  the  watershed  of  the 
reservoir  has  1,500  cubic  feet  more,  making  a  total  available  water 
supply  of  5,220  cubic  feet  per  minute.  The  water  is  diverted  from 
the  creek  and  runs  through  a  wooden  flume  3^  miles  long,  which 
is  6  X  8  feet  and  laid  on  a  grade  of  0.2  per  cent.  From  the  flume 


ANIMAS  PLANT 


177 


water  flows  into  a  natural  water-course  and  empties  into  a  reservoir, 
which  has  an  area  of  960  acres. 

The  reservoir  was  made  by  building  a  stone-and-timber  dam 
about  750  feet  long  and  55  feet  high,  with  a  foundation  33  feet  deep 
to  bedrock.  It  is  proposed  to  replace  this  dam  by  one  of  con- 
crete 100  feet  high  and  about  1,400  feet  long.  This  will  increase 
the  area  of  the  reservoir  to  1,161  acres.  When  the  concrete  dam 


FIG.  88. — ANIMAS  DAM. 

is  built,  the  company  expects  to  take  the  water  from  Lime  Creek 
into  the  reservoir,  which  can  be  done  by  building  another  flume  4 
miles  long.  When  the  water  from  Lime  Creek  is  added,  the  avail- 
able water  supply  will  be  double,  or  10,440  cubic  feet  per  minute. 
At  some  future  time,  as  the  demand  for  power  increases,  it  is  pro- 
posed to  use  the  water  from  the  Animas  River.  In  order  to  accom- 
plish this,  it  will  be  necessary  to  build  a  tunnel  8  miles  long,  and 
when  this  is  done  there  will  be  sufficient  water  for  developing 
some  38,000  H.P. 

From  the  reservoir  the  water  is  taken  in  a  38  X  56  inches 
wooden  flume  8,800  feet  long,  laid  on  a  grade  of  0.25  per  cent., 
which  empties  into  an  intake  reservoir.  The  intake  reservoir 
has  an  area  of  about  five  acres.  Its  dam  is  of  earth,  with  a 

12 


178      DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

concrete  core  wall  3  feet  thick  and  another  concrete  wall  at  the 
inner  toe.  At  present  it  is  30  feet  high  by  about  100  feet  long,  but 
it  is  to  be  raised  10  feet,  which  will  give  an  effective  head  of  970 
feet  at  the  power-house. 

The  pipe  enters  the  intake  reservoir  25  feet  below  the  surface 
of  the  water,  thereby  avoiding  any  possibility  of  ice  entering  or 
blocking  the  pipe.  In  front  of  the  pipe  is  located  the  usual 
screen  made  of  flat  bars  of  steel.  The  end  of  the  pipe  is  tapered 
to  60  inches  in  diameter;  where  it  emerges  from  the  dam  it  is  44 


FIG.  89. — ANIMAS  FLUME. 

inches,  and  has  a  gate  valve  and  a  lo-inch  standpipe  on  the  lower 
side  to  admit  air,  so  as  to  prevent  any  danger  of  collapsing  the 
pipe  in  case  the  valve  is  rapidly  closed.  The  standpipe  passes 
through  the  gate-house  and  is  enclosed  in  a  wood  flue.  The  heat 
from  a  stove  in  the  gate-house  passes  through  the  flue  and  around 
the  standpipe  to  prevent  the  water  in  it  from  freezing. 

It  would  appear  that  nature  had  intentionally  left  an  opening 
in  the  cliffs  for  a  pipe  line  to  come  down  from  this  reservoir  to  the 
power-house.  Starting  at  the  top,  where  the  elevation  is  987  feet 


ANIMAS  PLANT 


179 


above  the  station,  the  pipe  is  44  inches  in  diameter  by  3-16  in.  thick 
and  runs  for  some  800  feet,  on  a  slight  grade  over  the  mountain  to 
a  point  where  the  head  is  125  feet  and  the  pipe  is  thickened  to  J 
inches.  From  this  point  downward  the  metal  in  the  pipe  increases 


FIG.  90. — PIPE  LINE  AND  POWER-HOUSE. 

in  thickness  to  11-16  inches  and  the  diameter  changes  to  40,  36, 
and  34  inches,  there  being  an  equal  quantity  of  each  diameter. 
The  pipe  is  2,842  feet  long  and  is  double  riveted  in  the  longitudinal 
seams  and  single  riveted  in  the  girth  seams,  down  to  560  feet  head. 


l8o       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

From  this  point  it  is  double  riveted  in  the  longitudinal  seams  and 
single  butt-strapped  and  single  riveted  in  the  girth  seams  down 
to  a  point  where  the  head  is  975  feet,  and  from  there  to  the  bottom 
the  pipe  is  double  butt-strapped  and  triple  riveted  in  the  longi- 
tudinal seams.  The  riveted  joint  efficiency  is  82  per  cent.  The 
pipe  is  made  up  in  sections  30  feet  long  and  fitted  with  welded  steel 
angle  flanges.  The  flanges  are  bolted  together  with  combination 
copper  and  lead  gaskets  between  them.  The  gaskets  are  made 
with  one  ring  of  J-inch  copper  wire  just  inside  of  the  bolts,  then 
comes  a  lead  ring  3-16  inches  thick,  and  inside  of  this  a  5-16  inch 
lead  ring.  The  three  rings  are  held  together  in  places  by  solder 
and  make  a  very  substantial  and  perfectly  water-tight  joint.  The 
heaviest  sections  of  pipe  weigh  six  tons  each.  The  steepest  grade 
on  the  line  is  84  per  cent. 

At  the  power-house  and  lower  bends  the  pipe  is  thoroughly 
anchored  in  large  blocks  of  concrete,  each  of  sufficient  size  to  carry 
the  weight  of  the  pipe  above  it.  The  sections  of  pipe  at  the 
lowe/  end  were  tested  to  650  pounds  per  square  inch  before 
leaving  the  shops  of  the  company,  which  furnished  the  piping 
and  water-wheels.  The  pipe  was  hauled  up  the  hill  with  a  mine 
hoist  and  cable,  and  the  grade  was  so  steep  the  cable  could  not  be 
loosened  from  a  section  until  it  was  in  place. 

At  the  lower  end  of  the  pipe  line  there  is  a  cast- steel  Y,  taper- 
ing down  to  two  20- inch  branches  fitted  with  gate  valves  having 
by-passes,  and  roller  bearings  connecting  to  the  2o-inch  by-pass 
needle  nozzles  of  the  wheels.  The  nozzles  are  arranged  with  a 
system  of  toggle  levers  by  means  of  which  the  water  can  be  turned 
from  the  wheel  through  the  by-pass.  These  toggles  are  arranged 
so  that,  for  a  uniform  rotation  of  the  governor  shaft,  the  variation 
in  power  delivered  to  the  wheel  will  be  constant.  The  by-pass  is 
used  in  order  to  prevent  shock  to  the  pipe  in  case  the  load  is  sud- 
denly thrown  off  the  generator.  The  needle  which  controls  the 
supply  of  water  to  the  wheel  and  the  one  to  the  by-pass  are  connected 
by  means  of  a  right-and-left-hand  screw  so  that  their  relative  posi- 
tions can  be  changed  at  will  by  means  of  a  hand  wheel.  This  hand 


ANIMAS  PLANT 


181 


wheel  can  be  set  by  the  aid  of  a  predetermined  load  curve  and  re- 
duces the  waste  from  the  by-pass  water  to  a  minimum. 

The  wheels  are  8  feet  overhung  Pelton  wheels  one  on  each 
generator  shaft,  with  a  normal  capacity  of  3,000  H.P.  each  at 
300  r.p.m.,  but  capable  of  being  run  up  to  4,000  H.P.  The  wheel 
centres  and  the  buckets  arc  made  of  cast  steel.  Each  bucket  is 
bolted  to  the  wheel  centre  with  one  2j-inch  and  one  ij-inch  bolt, 
giving  ample  strength  to  permit  the  wheel  being  locked  and  full 


FIG.  91. — 3,000  H.P.   PELTON  WHEELS  AND  GENERATORS. 

stream  turned  on  or  allowed  to  run  as  fast  as  the  water  will  drive 
it  with  no  load  on.  The  shafts  are  fourteen  inches  in  diameter  at 
the  bearings  and  16  inches  at  the  rotors  or  fields.  They  are  hollow, 
with  5-inch  holes  through  which  water  is  made  to  circulate  to 
assist  in  keeping  the  bearings  cool.  The  bearings  are  14  X  42 
inch  water-cooled,  and  arc  babbitted  in  lower  half  only. 

The  wheels  are  controlled  by  oil-pressure  governors  with  two 
pumps,  arranged  so  that  one  can  furnish  power  for  either  or  both 
governors. 

The  generators  are  of  2,250  K.W. -capacity,  and  of  the  revolving- 
field,  three-phase,  6o-cycle  type,  with  the  exciter  armature  mounted 
on  the  shaft.  The  generator  voltage  is  4,000,  with  step-up  trans- 
formers and  line  voltage  of  50,000. 


1 82       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

There  are  six  water-cooled  oil  transformers  of  750-K.W. 
capacity  each.  Each  transformer  is  located  in  an  iron-and-con- 
crete  vault,  completely  closed,  so  that  in  case  of  fire  the  oil  cannot 
burn  and  damage  any  of  the  other  apparatus. 

The  switchboard  gallery  is  located  over  the  transformer  vaults. 


FIG.  92. — CROSS-SECTION  OF  POWER-HOUSE. 

The  generator  mains  run  up  through  brick  chambers  to  the  oil 
switches  and  circuit  breakers  and  then  to  the  generator  bus-bars. 
From  the  bus-bars  the  circuit  passes  down  to  the  transformers 
where  the  current  is  stepped  up  to  50,000  volts.  The  circuits  then 
go  to  the  high-tension  oil  switches  and  circuit  breakers,  and  from 
there  to  the  transmission  line.  The  switchboard  is  located  near 
the  front  of  the  gallery  and  fitted  with  the  usual  instruments,  to- 
gether with  a  voltage  regulator.  The  operator  in  front  of  the 
switchboard  has  all  of  the  machinery  in  full  view. 

The  transmission  line  is  built  of  three  cables,  each  composed 
of  six  No.  8  B.  &  S.  aluminum  wires  with  a  hemp  core  and  a  con- 
ductivity equal  to  No.  2  B.  &  S.  copper.  The  cables  are  arranged 


DRAMMEN  PLANT  183 

on  the  cross-arms  so  as  to  form  a  triangle  with  6-feet  sides.  The 
poles  are  pine,  36  feet  long,  and  set  6-feet  in  the  ground  250  feet 
apart.  The  longest  span  is  1,100  feet,  where  the  cables  stretch 
between  wooden  towers  and  span  an  arm  of  the  reservoir.  There 
is  a  substation  in  Silverton  with  transformers  for  stepping  down 
to  17,000  volts. 


HYDRO-ELECTRIC   PLANT   OF  THE   CITY  OF 
DRAMMEN,  NORWAY. 

Abstracted  from  the  Electrical  Reinew  o)  May   12,    1906. 

FOR  supplying  light  and  power  to  the  city  of  Drammen  and  the. 
surrounding  country  on  the  Drammen  Fjord,  located  some  twenty 
miles  southwest  from  Christiania,  the  water  of  the  Storelven  was 
dammed  at  the  waterfall  "  Gravfos"  and  utilized  in  the  power-house 
located  at  the  junction  of  the  Storelven  (the  upper  part  of  the  river 
Draven)  and  the  Suaramselvcn,  some  twenty  miles  above  the  city 
of  Drammen.  Preliminary  to  the  construction  of  the  power  plant 
it  was  necessary  to  build  a  branch  of  the  Drammen-Randsfjord 
Railway  from  Gjeithus  and  connecting  from  the  end  of  this  branch 
to  the  plant  by  wray  of  a  steel  bridge  over  the  "  Gravfos. " 

About  65  metres  (215  feet)  above  this  fall  a  concrete  dam 
is  constructed,  with  the  intake  canal  at  the  left  of  the  river- 
bed, provided  with  six  main  sluice  gates  operated  from  a  gallery 
above  the  intake.  Connecting  with  this  canal  is  a  tunnel  230  feet 
long  and  10  metres  (32.8  feet)  wide  at  the  bottom  with  an  arched 
roof  cut  in  the  mountain.  On  account  of  the  softness  of  the  rock 
it  was  found  necessary  to  line  this  tunnel  for  a  distance  of  27 
metres  (88 J  feet)  with  brick.  This  tunnel  leads  into  the  col- 
lecting basin,  which  it  was  also  found  necessary  to  line  with 
masonry.  The  tunnel  enters  one  side  of  the  collecting  basin, 
while  on  the  opposite  side  are  two  pressure  tunnels,  there  being 
space  for  a  third  one.  One  of  the  ends  of  the  basin  is  provided 
with  an  overflow  and  sluice  gate  to  drain  the  basin  in  case  of  an 


184       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

emergency.  All  sand  and  gravel  carried  down  to  the  basin  is  re- 
moved by  a  sand  trap  through  the  overflow  channel.  The  sand- 
trap  gates  and  also  the  emergency  gates  are  operated  from  a  point 
on  top  of  the  wall  of  the  basin.  Sluice  gates  are  installed  in  the 
pressure  tunnels,  only  one  of  which  is  at  present  in  use.  These 
tunnels  are  4  metres  (13.12  feet)  high  and  4.25  metres  (13.94 
feet)  wide  and  are  lined  with  masonry.  Two  turbines  arc  con- 
nected to  this  tunnel  by  means  of  two  short  steel  branch  penstocks, 
leading  from  one  main  penstock,  and  a  third  branch  penstock 
leads  to  the  two  exciter  units. 

As  the  available  water  supply  was  30  cu.  meters  (1056  cubic  feet) 


FIG.  93. — POWER-HOUSE. 

per  second  with  a  net  fall  of  14.5  metres  (47.5  feet),  a  development  of 
4,400  H.P.  was  possible.  This  energy  had  to  be  transmitted  over  a 
distance  of  35  kilometres  (21  miles)  and  distributed  to  two  harbor 
cities  spread  along  the  shores  of  the  fjord.  The  plant  was  designed 
to  generate  three-phase  alternating  current  at  a  potential  of  5,000 
volts,  which  is  stepped  up  to  20,000  volts  and  then  transmitted  to  the 


DRAMMEN  PLANT 


city  "entrance  of  Drammen,  where  this  secondary7  current  at  18,000 
volts  is  transformed  down  to  4,500  volts.  From  here  the  current 
is  distributed  to  a  number  of  smaller  transformer  substations, 
where  this  4,500  volts  is  again  stepped  down  to  220  volts,  at  which 


u      o        o        u        o 

FIG.  94. — PLAN  OF  POWER-HOUSE. 

potential  the  consumers  are  supplied.  The  feeder  systems  are 
installed  partly  overhead  and  partly  underground.  From  the  fore- 
going it  will  be  seen  that  the  installation  includes  a  generating  sta- 
tion, a  step-up  transformer  system,  a  long-distance  high-tension 
transmission  line,  a  step-down  transformer  station,  a  high-tension 
distributing  system,  step-down  transformer  substations  and  low- 
tension  distributing  systems.  The  hydraulic  plant  is. designed 
for  four  main  units  and  three  exciter  units,  having  at  one  end 
space  for  the  switchboard  and  step-up  transformers.  The  total 
length  of  the  plant  is  42  metres  (137.7  feet)  and  the  width  16 
metres  (52.4  feet)  with  an  extension  on  one  side  containing 
offices,  storerooms,  pump-room,  and  a  repair  shop.  The  entire 
building  up  to  the  generating-room  floor  is  of  concrete,  while 
the  upper  part  is  of  brick.  The  roof  trusses  are  of  steel  covered 
with  wooden  planking  and  corrugated  steel.  A  5o-ton  overhead 
crane  travels  the  length  of  the  generating-room,  but  not  over  the 


1 86       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

switchboard.  As  already  stated,  the  plant  is  designed  to  accom- 
modate four  main  units,  although  only  two  goo-H.P.  units  are  at 
present  installed  and  two  66-H.P.  exciter  units. 

Before  entering  the  building  the  penstock  is  divided  into  two 
parts,  each  of  2.1  metres  (6.88  feet)  diameter,  each  supplying  one 
of  the  main  goo-H.P.  units.  Iri^  addition  to  these  there  is  another 
third  branch  i  metre  (3.28  feet)  in  diameter  supplying  the  ex- 
citer units.  Each  of  the  main  pipes  is  equipped  with  a  butterfly 
valve.  To  operate  these  butterfly  valves  electric  motors  are  in- 
stalled in  the  pump-room,  while  the  valve  of  the  exciter  penstock 
is  operated  by  hand.  The  main  turbines  are  built  on  the  double- 
wheel  Francis  type,  making,  with  a  head  of  14.5  metres  (47.56 
feet)  and  214  r.p.m.,  900  effective  H.P.  Each  turbine  unit  is 


FIG.  95. — LONGITUDINAL  SECTION  OF  POWER-HOUSE. 

provided  with  a  flywheel.  Between  the  turbine  and  flywheels  is 
a  clutch  coupling.  Each  turbine  is  well  provided  with  hydraulic 
governing  devices.  For  switching  the  turbines  in  multiple  the 
operation  of  the  governor  is  controlled  from  the  switchboard  by 
an  electric  motor  mounted  on  the  side  of  the  governor. 


DRAMMEN  PLANT 


I87 


The  pressure  water  needed  for  the  governor  is  supplied  by  two 
7-H.P.  electrically  operated  pumps  installed  in  the  above-men- 
tioned pump-room  together  with  the  necessary  accumulator. 

The  exciters  are  also  driven  by  Francis  turbines,  but  of  the 
single-wheel  type.  These  turbines  are  also  equipped  with  fly- 


FIG.  96. — TRANSVERSE  SECTION  OF  POWER-HOUSE. 

wheels  forming  part  of  the  coupling  between  the  turbine  and  gener- 
ator. The  couplings  are  not  of  the  rigid  type,  but  are  insulated 
flexible  couplings.  These  turbines  are  also  equipped  with  hy- 
draulic regulating  mechanism,  but  the  pressure,  however,  is  sup- 
plied by  the  head  in  the  penstock,  thus  avoiding  the  necessity  of 
pumps,  as  is  the  case  with  the  main  units.  The  small  turbines, 
with  maximum  water  supply,  have  an  efficiency  of  75  per  cent, 
while  the  main  units  under  the  same  conditions  have  the  same 
efficiency.  With  0.8  load  the  efficiency  is  71  per  cent  and  with 
0.6  load,  70  per  cent. 

With  a  sudden  decrease  in  load  from  full  to  no  load  the  varia- 
tion in  speed  will  not  exceed  15  per  cent,  while  with  a  variation  of 
25  per  cent  in  load  the  flywheel  holds  the  variation  in  speed  down 
to  only  2  per  cent. 


1 88       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

The  alternators  are  of  the  Oerlikon  type,  750  K.W.,  5,000  volt 
three-phase,  50  cycles,  and  are  coupled  to  the  turbine  shafts  by 
means  of  insulated,  flexible  belt  couplings.  The  magnet  frame  is  in 
two  parts,  divided  horizontally,  with  laminated  poles  bolted  to 
the  frame.  At  full  load  and  power  factor  =  i  the  efficiency  is  94 
per  cent,  while  with  power  factor  =  0.8  the  efficiency  is  93  per 
cent.  In  decreasing  from  full  load  to  no  load  the  potential  in- 
crease in  the  former  case  is  7  per  cent  and  in  the  latter  case 
15  per  cent.  The  above  figures  allow  for  the  energy  of  excita- 
tion, which  at  full  load  is  7  K.W.  with  power  f actor  =i  and  13 
K.W.  with  power  factor =0.8.  The  maximum  temperature  in- 
crease after  a  24-hour  full-load  run  does  not  exceed  40°  C.  The 
64-K.W.  exciter  sets  are  no-volt,  shunt-wound,  direct-current- 
generators,  each  connected  by  a  flexible  coupling  to  the  flywheel  of 
its  turbine  shaft,  as  already  mentioned,  and  operate  at  650  r.p.m. 

From  the  generators  to  the  switchboard,  cables  are  laid  in  a 
tunnel  below  the  floor,  three,  70  sq.  mm.,  iron-bound,  lead-covered 
cables  leading  from  each  machine. 

The  switchboard  is  placed  on  the  end  wall  of  the  plant 
and  is  two  stories  high,  the  lower  part  on  the  generator-room- 
floor  level  being  occupied  with  the  transformers  and  rheostats, 
while  the  upper  part  is  taken  up  with  high-tension  (20,000  and 
5,000  volt)  fuses,  switching  devices,  measuring  instruments,  etc. 
Above  this  is  a  small  gallery  where  are  located  the  bus-bars 
and  horn  lightning  arresters.  The  switchboard  is  completely 
equipped  with  the  most  modern  apparatus  and  the  entire  wiring 
layout  made  with  a  view  to  convenience,  flexibility,  and'  simplicity. 
The  current  from  each  generator  is  measured,  and  the  total  current 
supplied  to  the  5,000- volt  bus-bars  again  measured  by  recording 
instruments  before  feeding  the  step-up  transformers.  Current  at 
20,000  volts  is  then  led  out  over  a  line  protected  by  two  horn  light- 
ning arresters,  on  each  phase  arranged  in  parallel,  and  also  choke 
coils.  In  addition  to  this,  a  continuous  flow  of  water  prevents 
the  potential  from  rising  above  20,000  volts.  If  the  potential  ex- 
ceeds this  amount  it  is  grounded  through  the  water. 


DRAMMEN   PLANT 


i89 


For  switching  the  generators  in  parallel  a  voltmeter  switch,  a 
phase  voltmeter,  and  synchronizing  lamp  are  provided.  A  small 
regulating  motor  is  controlled  from  the  switchboard. 

The  switchboard  is  designed  to  accommodate  the  complete 
installation,  although  at  present  the  apparatus  for  only  two  units 


Until  Lightning 
Arrester 


FIG.  97. — SECTION  THROUGH  TRANSFORMER  AND  SWITCH  ROOM. 


I QO       DEVELOPMENT   AND    DISTRIBUTION   OF   WATER   POWER 

and  the  auxiliaries  is  installed.  The  board  is  made  of  white  marble, 
mounted  on  an  iron  frame. 

The  switch  system  for  the  transformers  consists  of  two  separate 
systems,  one  for  5,000  volts  lying  in  the  generator-room,  and  the 
other  for  20,000  volts  in  the  transformer-room.  The  transformers 
are  mounted  on  wheels,  so  that  they  may  be  moved  onto  low 
platform  cars  and  carried  into  the  repair  shop.  An  air  duct  ex- 
tends under  the  transformers  for  ventilation,  with  a  motor-driven 
fan  at  the  end. 

The  feeder  system  is  designed  to  transmit  1,800  H.P.  with  a 
drop  in  potential  of  n  per  cent.  The  length  of  the  feeder 
system  is  about  21  miles  and  consists  of  three  hard-drawn  copper 
wires  with  a  sectional  area  of  25  sq.  mm. 

The  common  method  of  carrying  these  wires  is  on  wooden  poles 
having  three  cross-arms  in  order  to  carry  six  insulators  for 
two  systems.  Three  insulators  only,  are  at  present  in  place. 
They  are  so  placed  that  each  cross-arm  has  one  insulator.  This 
is  done  in  order  to  allow  a  turn  of  one-third  in  the  relative  position 
of  the  feeders,  which  takes  place  once  in  three  and  one-half  miles, 
so  that  in  the  whole  run  the  cables  are  twisted  twice.  The  poles 
are  placed  about  210  feet  apart.  In  crossing  streets,  streams,  etc., 
protective  wire  nets  are  placed  under  the  feeders,  so  that  a  broken 
wire  may  not  drop  to  the  ground. 

Wooden  poles  are  used  throughout  most  of  the  run;  lattice- 
work iron  poles,  however,  are  used  in  several  cases.  These  poles 
are  of  the  requisite  height  and  are  thoroughly  crcosoted  and  pro- 
tected by  cast-iron  caps.  The  wires  are  carried  on  delta-shaped 
brown  porcelain  insulators  bolted  to  the  cross-arms.  The  cross- 
arms  are  braced  by  angle  irons.  Below  this  high-tension,  2O,ooo-volt 
system  for  a  certain  distance  is  carried  the  5,ooo-volt  feeder  on 
porcelain  insulators  mounted  on  iron  brackets.  Twenty- six  inches 
below  these  are  placed  the  telephone  lines.  Ten  sectional  cut-outs 
are  installed,  enabling  the  operator  to  disconnect  certain  districts. 
At  the  crossing,  over  the  railway,  a  roofed  steel  structure  is  pro- 
vided to  carry  the  feeders. 


DRAMMEX  PLANT 


There  is  at  present  one  transformer  station  for  reducing  the 
potential  from  18,000  to  4,500  volts.  On  entering  the  station  the 
wires  are  equipped  with  two  parallel  switches  and  horn  lightning 
arresters  for  each  phase.  In  connection  with  the  arresters 
there  is  an  induction  coil  in  each  phase.  From  the  substation, 
three  cables  and  one  air  line  lead  out  at 
a  potential  of  4,500  volts  for  the  high- 
tension  distribution  system.  A  small 
auxiliary  transformer  is  installed  to  fur- 
nish power  at  220  volts  for  lighting  the 
station  and  to  operate  the  transformer 
blower.  As  the  transformer  station  is  a 
three-story  building;  the  main  floor  con- 
tains the  transformers,  blower,  etc.,  the 
second  floor  the  switching  system  for  the 
outgoing  feeders,  and  the  third  floor  the 
lightning  arresters  for  the  incoming  and 
outgoing  feeders.  The  transformers  are 
of  the  same  design  as  in  the  main  power- 
house. 

The  high-tension  distribution  system 
leads  to  two  transformer  substations  be- 
ing carried  on  the  same  poles  as  the 
high-tension  transmission  line.  The 
wire  is  2O-sq.  mm.  hard-drawn  copper, 
mounted  on  brownglazed  porcelain  in- 
sulators. The  greater  part  of  the  high- 
potential  distribution  system  is  that 
carried  underground  on  cables  for  about 
eight  miles.  From  the  substation  two 

cables  run  to  each  of  the  two  halves  of  the  city  on  the  opposite  side 
of  the  river  and  fjord.  These  cables  are  paper-insulated  in  a  lead 
sheathing,  filled  with  jute,  and  iron  bound.  At  the  sub-transformer 
stations  the  potential  is  stepped  down  from  4,500  to  220  volts. 
There  are  altogether,  14  tiansformer  stations,  12  of  which  are  in 


FIG.  98. — POLE-HEAD. 


1 92       DEVELOPMENT   AND   DISTRIBUTION  OF   WATER   POWER 

the  form  of  cylindrical  steel  towers  about  5^  feet  in  diameter  and 
some  20  feet  high,  while  the  two  others  are  of  brick.  The  former 
stations  rest  upon  solid  concrete  foundations  and  are  provided  with 
doors  to  give  access  to  the  different  apparatus.  Special  care  is  taken 
for  good  air  circulation;  the  air  entering  at  the  bottom  rises  and 
is  discharged  below  the  top  hood. 

The  high-  and  low-tension  systems  are,  of  course,  distinctly 
separate,  and  so  also  are  the  light  and  power  systems.  In  order 
to  simplify  the  wiring  as  much  as  possible,  the  three  high-tension 
bus-bars,  which  are  of  aluminum,  are  mounted  directly  on  the  fuses. 
On  the  low-tension  side,  the  feeders  run  down  to  a  three-pole  knife 
switch  and  to  the  fuses.  Here,  also,  the  bus-bars  are  mounted 
directly  on  the  fuses.  The  iron  frame  of  the  stations  as  well  as  the 
transformer  frames  are  positively  grounded  with  a  copper  wire. 

The  masonry  buildings  are  made  of  rough  stone  and  well  sup- 
plied with  natural  light  and  also  designed  for  air  circulation.  The 
wires  of  the  4, 500- volt  system  enter  the  station  through  glass  plates, 
passing  through  induction  spools  and  fuses  to  the  transformers. 
The  system  is  protected  by  three,  horn  lightning  arresters.  The 
other  equipment  is  the  same  as  for  the  iron  towers. 

The  low-tension  distributing  system  consists  of  overhead  air 
lines  and  underground  cables,  the  latter  being  laid  in  trenches 
28  inches  deep  and  covered  by  tiling.  The  overhead  lines  do 
not  run  directly  from  the  transformer  stations,  but  are  connected 
from  the  underground  feeders,  at  which  points,  small  iron  lat- 
ticed poles  are  erected.  These  poles  are  surrounded  by  an  iron 
sheathing  6J  feet  high,  provided  with  a  door  to  give  access  to  the 
fuses,  etc.  From  the  fuses  the  feeders  rise  to  the  top  of  the  pole, 
which  is  also  surrounded  by  sheet  iron  behind  which  the  induc- 
tion coils  are  arranged.  The  lightning  arresters  are  installed  out- 
side of  this  casing.  The  arresters  and  towers  are  grounded  by  a 
common  copper  wire.  From  these  distributing  towers  the  wires 
lead  to  the  various  consumers. 


GREAT  FALLS  PLANT  193 

THE    GREAT    FALLS    STATION   OF   THE    SOUTHERN 
POWER  COMPANY. 

Abstracted  jrom  the  Engineering  Record  oj  May  18,  1907. 

THE  Southern  Power  Company  owns  or  controls  in  all  nine 
water-power  sites  in  the  so-called  Piedmont  Section,  embracing  the 
sand-hill  district  extending  from  the  foot  of  the  Blue  Ridge  moun- 
tains to  the  fall  line,  a  distance  averaging  probably  120  miles. 
One  capable  of  development  for  12,000  H.P.  lies  on  the  Broad 
River  of  the  Carolinas  equidistant  from  Gaffney  and  Blacksburg, 
S.  C.,  while  another  is  located  on  the  \Yateree  River,  of  which  the 
Catawba  River  is  the  principal  tributary.  This  one  is  capable  of 
development  for  20,000  H.P.  All  others  are  on  the  Catawba 
River.  The  aggregate  of  these  powers  will  amount  to  145,0x30 
H.P.,  which  will  be  transmitted  to  cover  a  territory  over  150  miles 
long  and  about  100  miles  in  width. 

The  Great  Falls. — The  Great  Falls  of  the  Catawba  consists  of  a 
series  of  falls  and  shoals  having  a  total  head  of  176  feet  in  a  distance 
of  about  8  miles,  the  development  of  which  will  require  three 
separate  plants. 

The  lowest  of  these  necessitates  the  construction  of  a  dam 
across  the  river  just  below  the  mouth  of  Rocky  Creek,  at  which 
point  there  is  available  a  drainage  area  of  4,450  square  miles; 
a  development  of  60  feet  is  here  feasible,  which  head  backs 
water  to  the  elevation  of  tail  water  in  the  middle  development. 

The  highest  development  with  a  drainage  area  of  3,900  square 
miles  will  be  effected  by  the  construction  of  a  dam  immediately 
above  the  mouth  of  Fishing  Creek.  This  plant  will  operate  under 
a  head  of  40  feet,  and  its  tail-water  elevation  will  correspond  to 
head  water  for  the  middle  development. 

The  middle  development  with  a  head  of  72  feet  receives  the 
run-off  from  the  drainage  area  of  4,200  square  miles,  and  is  known 
as  the  Great  Falls  Station,  the  subject  of  this  description. 

From  observations  made  under  various  auspices  it  has  been 


194 


DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 


deduced  that  although  the  minimum  flow  of  the  rivers  in  this  particu- 
lar locality  averages  about  J  cubic  foot  per  second  per  square  mile 
of  drainage  area  and  for  eight  months  in  the  year  about  J  cubic 

foot  may  be  depended 
upon,  the  flood  volume 
against  which  precaution 
must  be  taken  in  design 
is  somewhat  below  50 
cubic  feet  per  second  per 
square  mile,  such  flood- 
water  flow  being  an  ex- 
ceedingly high  one,  and, 
it  is  thought,  the  greatest 
on  record  with  the  U.  S. 
Geological  Survey. 

This  development 
consists  essentially  of  a 
low  spillway  dam  at  the 
head  of  Mountain  Island 
to  deflect  the  water  into 
the  western  channel. 
Flowing  through  this 
channel  nearly  to  the 
foot  of  the  island,  it  is 
then  forced  through  the 
head-gates  -of  the  canal 
g;  by  another  spillway  dam. 
0  An  extension  of  this  dam 
*  serves  as  an  overflow 
weir  between  the  canal 
and  the  river.  From  this 
point  the  stream  is  car- 
ried by  a  canal  through 
a  natural  valley  about 
ij  miles  to  the  power- 


GREAT  FALLS  PLANT 


195 


house  and  retaining  bulkhead  built  across  the  valley,  while  below 
the  power-house  t  he  tail-race  carries  off  the  spent  waters  J  mile  to 
Rocky  Creek,  in  which  channel  it  is  again  carried  to  the  river-bed. 
Canal  Head-works. — The  deflecting  dam  at  the  head  of  Moun- 
tain Island  is  an  ogee  section  overflow  dam  only  7  to  8  feet  high, 


FIG.   ico. — DIVERTING  DAM  AND  CANAL  SPILLWAY. 

the  fall  utilized  for  this  development  occurring  almost  wholly  in 
the  western  channel,  and  in  the  dip  of  the  valley  through  which 
the  canal  is  carried  to  Rocky  Creek. 

The  main  spillway  at  the  head-gate  works,  438.85  feet  long  on 
the  crest  line  with  an  average  height  of  about  30  feet,  has  a  batter 
of  i :  10  on  the  upstream  face  and  an  ogee  downstream  face.  The 
corresponding  width  at  the  base  of  the  section  is  about  41  feet. 
This  spillway,  in  connection  with  the  diverting  spillway  at  the  head 
of  Mountain  Island  is  designed  to  carry  safely  a  flood  overflow 
corresponding  to  50  cubic  feet  per  second  per  square  mile  of  drain- 


196       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

age  area,  which  volume  of  flood  water  will  cause  overtopping  of 
the  crest  of  the  dam  to  a  depth  of  14^  feet. 

The  curve  on  the  downstream  face  was  determined  by  plotting 
the  parabolic  curve  for  the  average  velocity  of  the  film  of  over- 
flowing water  increased  by  an  assumed  initial  velocity  of  eight  miles 
per  hour,  and  so  fitting  the  masonry  to  this  curve  as  to  intercept 
the  nappe,  breaking  the  velocity  near  the  top  and  thus  insuring 
contact  of  the  sheet  of  water  on  the  entire  downstream  face.  The 
weight  of  masonry  was  assumed  to  be  125  pounds  per  cubic  foot. 
An  upward  pressure  equal  to  two-thirds  of  the  head  at  the  heel  of 
the  section  and  decreasing  to  zero  at  the  toe  was  assumed  to  exist, 
and  there  was  also  considered  to  offset  this  pressure  the  weight  of  the 
overflowing  sheet  of  water  tending  to  increase  the  stability  of  the 
dam.  Under  these  assumptions  the  section  shows  a  safety  factor 
of  two  for  the  most  severe  conditions,  with  increasing  stability  as 
the  conditions  approach  the  normal  stage. 

The  spillway  in  the  canal,  similarly  designed,  and  521.2  feet 
long  on  the  crest,  averages  about  36  feet  in  height,  corresponding 
to  which  height  the  base  has  a  width  of  about  37  feet  9  inches. 
The  crest  of  this  weir  is  one  foot  higher  than  that  of  the  main 
spillway  and  its  length  is  such  that,  with  the  worst  conditions  of 
flood  that  may  be  predicted,  it  will,  when  overtopped  to  a  depth 
of  8  feet,  carry  off  all  the  water  that  the  canal  head-gates  will 
vent. 

These  spillways,  the  head-gate  masonry,  and  all  heavy  bulkheads 
were  built  of  concrete  masonry,  in  which  are  embedded  displace- 
ment stones  as  large  as  could  be  handled  by  the  derricks.  All 
masonry  is  founded  on  bed  granite  of  a  close  and  uniform  texture. 
Sectional  forms  were  used  to  the  greatest  practicable  height,  the 
upper  curve  being  then  finished  by  hand  and  template. 

The  concrete  was  mixed  largely  in  the  proportions  of  one  part 
of  Edison  Portland  cement  to  two  parts  of  sharp,  creek  sand  ob- 
tained on  the  building  site  and  five  parts  of  crushed  granite,  the 
run  of  the  crusher  having  been  used  throughout. 

The  head-gate  masonry  supports  a  set  of  coarse  racks  and  has 


GREAT  FALLS  PLANT 


I97 


in  it  ten  ways  16  feet  wide  and  i8J  feet  high  with  full-centred  arch 
tops.  These  gate  openings  are  separated  by  piers  5  feet  in  width. 
This  section,  averaging  about  45  feet  in  height,  is  8  feet  wide  on 
top,  and  the  downstream  side  is  battered  3  on  i.  The  piers  are 
extended  on  the  downstieam  side  to  form  buttresses,  which  are 
5  feet  wide,  3  feet  long  on  a  level  with  the  top  of  the  main  wall,  and 


FIG.   101. — SECTION  OF  SPILLWAY  OF  MAIN  DAM. 

battered  2  on  i.  Piers  are  also  carried  out  on  the  upstream  side 
for  the  support  of  the  rack  structure.  These  are  3^  feet  long  on 
top,  this  being  6  feet  below  the  top  of  the  main  wall,  and  are  bat- 
tered 12  to  5,  giving  for  the  section  a  total  width  at  the  base  of  the 
gate  opening  of  about  47  feet. 

The  gate  frames  secured  into  this  masonry  are  built  of  standard 
structural  steel  shapes.  They  are  of  the  same  dimensions  as  those 
used  for  the  gates  of  the  turbine  intake  flumes,  and  it  was  contem- 
plated using  the  turbine  head-gates  in  these  frames  for  construction 


198       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

purposes.  Temporary  gates  were,  however,  later  built  of  timber 
for  this  purpose. 

In  the  event  of  placing  gates  in  these  frames  it  might  become 
necessary  to  relieve  the  pressure  upon  them  before  raising,  and  for 
that  purpose  a  by-pass  has  been  built  through  this  masonry  at 
the  shore  end.  The  gate  is  of  timber  and  is  operated  by  a 
Smith  gate  hoist. 

For  the  purpose  of  draining  the  low  point  immediately  below 
these  gates,  a  4  X  5 -foot  sluice  gate  was  built  into  the  bulkhead, 
discharging  below  the  spillway. 

The  racks  protecting  these  waterways  are  coarse,  being  built 
up  of  f -inch  grid-bars,  5  inches  deep,  spaced  3  inches  centre  to  centre, 
and  separated  by  cast-iron  spacers  of  such  design  as  to  prevent 
twisting  of  the  bars  under  shock.  These  grid-bars  are  supported 
by  a  structural  steel  frame  which  in  turn  is  supported  by  steel 
members  built  into  the  rack  piers.  This  entire  rack  structure 
was  designed  of  such  strength  as  to  withstand  any  pressures  that 
might  occur  with  a  full  head  of  water  against  a  completely  clogged 
rack.  The  racks  were  set  on  a  batter  of  12  to  5,  so  that  logs  and 
debris  that  might  lodge  against  them  should  be  forced  to  the  top, 
whence  they  might  be  piked  to  a  sluiceway  3  feet  deep  and  8  feet 
wide  left  in  the  spillway  section  for  that  purpose.  There  have  been 
left  in  this  sluiceway  grooves  for  the  accommodation  of  stop-planks 
should  such  economy  of  water  become  necessary. 

Construction  of  Head-works  and  Canal. — The  method  employed 
in  the  prosecution  of  this  work  was,  in  general,  as  follows:  Coffer- 
dam No.  i  was  built  deflecting  all  the  water  to  the  deeper  channel. 
The  block  of  masonry  marked  A  was  then  built.  These  coffer- 
dams consisted  of  log  cribs  filled  with  stone  and  sheathed  top  and 
sides.  The  building  of  blocks  B  and  C  was  then  undertaken, 
whereupon  cofferdam  No.  2  was  built,  and  when  completed  coffer- 
dam No.  3  was  built.  Then  all  the  head-gates,  except  those  in  the 
last  two  frames,  were  closed,  and  cofferdam  No.  i  was  opened  and 
the  water  was  vented  through  sections  E  and  F.  Temporary  gates 
were  then  placed  in  the  vent  E,  but  a  flood  at  this  time  tore  out 


GREAT  FALLS  PLANT 


199 


the  gate  pier,  and  necessitated  the  building  of  cofferdam  No.  4, 
within  which  this  closure  was  effected.  The  two  remaining  head- 
gates  were  then  placed  in  the  frames,  and,  temporary  gates  having 


been  placed  in  the  frames  of  vent  F,  the  final  closure  was  made. 
In  making  the  closure,  section  D,  nearly  200  feet  long  and  contain- 
ing about  6,000  yards  of  masonry,  was  built  in  nine  days  and  nights. 


20O       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

For  carrying  the  water  from  this  point  to  the  power-house  it 
was  necessary  to  excavate  but  little  material  to  secure  a  hydraulic 
grade  line  from  the  bottom  of  the  canal  gates  to  a  point  4^  feet 
lower  at  the  power-house. 

Such  excavation  as  was  necessary  to  secure  a  cross- section  with 
a  base  of  100  feet  and  side  slopes  in  rock  of  2  to  i  and  in  earth  of 
i  to  2  amounted  to  but  195,000  cubic  yards,  for  a  total  length 
7,250  feet,  and  all  of  this  material  was  necessary  for  filling  in  a 
gap  existing  between  the  valley  and  the  river. 

The  site  of  the  fill  was  prepared  by  clearing  off  all  vegetable 
matter  along  a  strip  100  feet  wide,  and  on  this  strip  a  puddle  of 
selected  material  was  placed. 

Station  Intakes. — At  the  lower  end  of  the  canal  the  water  is 
impounded  by  a  concrete  retaining  wall  or  bulkhead  having  a 
width  on  top  of  8  feet,  a  vertical  upstream  face  and  a  downstream 
face  battered  1.75  to  i,  the  height  in  the  centre  of  the  valley  being 
about  90  feet.  This  section  is  largely  increased  in  that  portion 
opposite  the  power-house,  for  here  there  are  built  through  the  bulk- 
head the  intake  flumes  for  the  turbines,  the  cases  of  which  are  also 
built  into  this  masonry,  and  the  power-house  is  built  immediately 
below  the  bulkhead,  forming  virtually  a  part  of  it. 

Through  this  masonry,  carrying  past  either  end  of  the  power- 
house, there  have  also  been  constructed  two  trashways  for  by-pass- 
ing leaves  and  small  debris  from  .the  racks.  These  are  48  inches  in 
diameter,  built  of  riveted  steel  pipe  and  closed  by  sluice  valves. 
Into  these,  by  a  manhole  and  check  valve,  there  is  also  carried  storm 
water  off  the  side  slope  of  the  valley. 

Before  the  water  reaches  the  head-gates  of  the  turbine  intake 
it  is  against  passed  through  a  set  of  racks  similar  to  those  at  the 
head  of  the  canal,  except  that  these  are  finer,  the  grid-bars  con- 
sisting of  J-inch  bars  4  inches  deep,  spaced  ij  inches  centre  to 
centre.  Provision  has  been  made  for  the  attachment  of  a  power- 
operated  rack-cleaning  device,  which  will  have  to  be  installed  a 
few  years  hence. 

After  passing  these  racks  the  water  is  controlled  in  its  passage 


GREAT  FALLS  PLANT 


201 


to  the  turbines  by  structural- steel  gates.  Eight  of  these  for  the 
generating  units  are  built  of  6-inch  I-beams,  and  are  covered  with 
|-inch  steel  plate  on  the  outer  side.  On  the  inner  side  they  have 
bronze  running  strips  at  the  sides  and  opposite  the  supporting 


202        DEVELOPMENT   AND    DISTRIBUTION   OF   WATER    POWER 

beams  in  the  gate  frame,  while  machined-steel  bearing  plates  at 
top  and  bottom  insure  tightness  when  the  gates  are  closed.  Each 
of  these  gates  is  provided  with  two  9  X  1 4-inch  filling  gates  for 
reducing  the  pressure  before  raising,  these  being  hand-operated 
from  the  top  of  the  bulkhead.  The  gates  are  suspended  upon 
steel  stems,  each  built  up  of  an  8-inch,  1 8-pound  I-beam,  and  a 
9-inch,  20-pound  channel,  and  to  the  latter  is  secured  the  pinion 
rack  engaging  with  the  gate  hoist. 

The  gates  are  operated  by  a  multiple  spur  and  worm  gear  off 
a  shaft  actuated  by  a  motor  from  a  point  in  its  middle.  The  motor 
is  stationed  in  a  small  house  on  top  of  the  bulkhead,  the  leads  for 
it  being  carried  in  vitrified  conduit  to  a  switch  box  in  the  tunnel 
and  thence  to  the  switchboard.  Speaking-tubes  are  carried  from 
this  house  and  also  from  various  points  in  the  transformer-house 
to  the  operator's  desk  in  the  power-house.  On  account  of  the  great 
initial  torque  required,  a  direct-current  compound-wound  motor 
with  a  weak  shunt  field,  operating  from  the  exciter  circuit  at  250 
volts,  was  selected  for  this  service.  This  is  practicable  since  the 
exciter  plant  is  of  a  capacity  largely  in  excess  of  that  required  for 
the  mere  excitation  of  the  generators.  By  the  use  of  pin  clutches 
it  is  possible  to  operate  any  or  all  gates  at  one  time.  The 
clutches  must,  of  course,  be  thrown  in  while  the  shaft  is  at  rest. 
Provision  has  also  been  made  for  operating  any  of  the  gates  by 
hand. 

The  two  gates  for  the  exciter  intakes  are  similar  to  those  just 
described,  except  that  they  are  framed  out  of  4-inch  I-beams,  the 
stems  being  composed  of  a  6-inch  12  J  pound  I-beam  and  a  9-inch 
i3j-pound  channel,  and  but  one  9  X  1 2-inch  filling-gate  is  provided. 
They  are  raised  by  hand-operated  mechanism.  All  these  gates 
slide  in  heavy  frames  built  of  structural-steel  shapes  anchored  into 
the  masonry  of  the  bulkhead  wall.  Directly  behind  the  gate  frames, 
but  not  rigidly  attached  to  them,  commence  the  intake  flumes  or 
feeder  pipes  for  the  water-wheels.  These  are  made  of  f-inch  boiler 
plate  stiffened  by  6  X  3  J  X  f-inch  angles,  rive  ted  around  it.  These 
flumes  taper  down  from  the  head-gates,  where  they  are  16  feet  wide 


GREAT  FALLS  PLANT  203 

by  i8J  feet  high  with  semicircular  ends,  to  16  feet  in  diameter  at 
the  mouthpiece  of  the  turbine  case. 

Turbines. — There  are  ten  units,  each  consisting  of  a  pair  of 
horizontal  twin  turbines  with  top  inlet  and  centre  discharge. 
Eight  of  these  are  required  to  furnish  5,200  H.P.  at  225  r.p.m. 
under  a  head  of  72  feet. 

Of  these  units  two  are  a  pair  of  48-inch  wheels  enclosed  in  a  cast- 
iron  wheel  case  mounted  in  a  turbine  case  of  y-i6-inch  boiler  plate 
riveted  to  cast-iron  heads.  The  latter  are  stiffened  against  shocks 
by  four  2j-inch  Norway-iron  rods  extending  from  the  front  to  the 
rear  head. 

In  the  feeder  pipe  and  over  the  centre  of  the  turbine  is  a  man- 
hole, just  inside  which  is  an  eye-bolt  for  the  suspension  of  blocks 
for  handling  turbine  parts.  Pressure  and  air  vent  pipes  12  inches 
in  diameter  run  up  through  the  bulkhead. 

The  draft  tubes  are  8  feet  10  inches  in  diameter  at  the  wheel 
case,  being  flared  at  the  bottom  to  a  width  of  18  feet,  the  ends 
being  semicircular  and  of  4  feet  5  inches  radius.  The  top  of  the 
mouth  is  sprung  to  form  an  arch  2  inches  high  to  prevent  any 
possible  collapse  of  the  metal  away  from  the  masonry.  These 
tubes  are  fabricated  from  y-i6-inch  plate  and  are  stiffened  in  the 
same  manner  as  the  intake  flumes. 

The  plates  of  the  upper  1 2  feet  of  the  draft  tube  from  the  saddle 
down  are  butt- jointed  and  strap-covered  on  the  outside  with  coun- 
tersunk rivets  on  the  inside.  Below  these  plates  the  joints  are  tel- 
escopic, with  the  lap  in  the  direction  of  the  flow  of  water.  In  the 
heads  of  the  turbine  case  are  removable  crown  plates  of  such  size 
as  to  permit  removal  of  any  part  of  the  work  inside  the  flumes. 

Should  it  become  necessary,  the  turbine  cases  may  be  drained 
by  valves  operated  from  the  power-house.  Check  valves,  for  re- 
moval of  any  water  seeping  into  the  power-house,  are  provided- be- 
fore each  unit  in  a  sump,  which  extends  the  entire  length  and  in 
front  of  all  the  wheel  cases. 

Vacuum  gauges  are  provided  for  all  draft  tubes.  The  draft 
head  in  these  wheels  is  22  feet,  and  the  draft  tubes  are  submerged 


2O4     DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

5  feet,  which  depth  was  deemed  necessary  to  permit  drawing  off 
the  pond  on  the  lower  development. 

The  runner  of  each  wheel  is  of  bronze  and  mounted  on  a 
shaft  30 \  feet  long  made  of  forged  nickel-steel;  it  is  9,  10,  and  n 
inches  in  diameter,  with  a  flange  coupling  keyed  to  it  for  connec- 
tion to  its  generator.  This  shaft  is  supported  on  the  outside  of 
the  turbine  case  by  ring-oiling,  ball-and-socket  bearings,  the  one 
in  the  power-house  being  made  to  harmonize  in  appearance  with 
the  bearings  of  the  generators. 

A  special  feature  of  this  plant  is  the  construction  of  a  tunnel 
extending  the  length  of  the  power-house  through  the  bulkhead  and 
just  back  of  the  turbine  cases.  By  this  method  of  construction  the 
usual  outboard  water-bearing  is  replaced  by  an  oil  bearing  which 
may  be  inspected  at  will,  and  the  removal  of  water-wheel  parts  is 
also  greatly  facilitated.  This  tunnel  is  10  feet  in  width  and  has  a 
segmental  arch  top,  in  which  is  anchored  an  I-beam  trolley  for 
carrying  material  to  and  from  the  power-house,  into  which  the  tun- 
nel opens.  Ventilation  is  here  provided  by  three,  1 2-inch  air  flues 
to  the  top  of  the  bulkhead.  The  water-wheel  shaft  extends  into 
this  tunnel  through  a  cast-iron  head  similar  to  that  in  the  power- 
house. 

The  outer  bearings  are  ring-oiling  ball-and-socket  bearings  of 
the  propeller  type.  The  pedestal  boxes  are  rigidly  connected  to 
the  head,  being  designed  to  take  up  the  end  thrust  of  the  water- 
wheels.  The  flow  of  water  to  these  wheels  is  regulated  by  cylinder 
gates.  All  racks  and  pinions  for  the  gatework  are  placed  on  the 
outside  of  the  turbine  case.  Hand  regulation  is  provided  for  these 
units  separate  from  that  of  the  governors. 

The  guaranteed  efficiency  of  each  of  these  units  is  determined 
by  a  curve  passing  through  the  following  points: 

Discharge Full         I         t         f         $ 

Efficiency  per  cent 81       82       81        74       68 

Six  of  the  larger  units  are  set  in  a  turbine  case  of  7-1 6-inch  plate, 
15  feet  in  diameter  and  19  feet  long.  In  this  case  the  cast-iron  heads 
are  stayed  across  the  wheel  case.  The  feeder  pipe  is  i8J  X  16 


GREAT  FALLS  PLANT  205 

feet  at  the  intake  gates,  and  tapers  to  15  feet  in  diameter  at  the  mouth 
piece  of  the  turbine  case. 

The  draft  tubes  are  n  feet  in  diameter  at  the  base  of  the  wheel 
case,  and  flare  to  18  feet  3  inches  by  n  feet  2  inches  at  the  lower 
end.  Two  of  these  units  are  provided  with  bronze  runners  53 
inches  in  diameter,  and  four  have  runners  of  special  cast  iron,  the 
latter  being  guaranteed  against  failure  or  undue  wear  for  a  period 
of  five  years.  The  gates  are  of  the  register  type,  being  nearly  bal- 
anced, with,  however,  a  tendency  to  close. 

The  shaft  is  of  forged  steel  9,  n,  and  13  inches  in  diameter,  and 
has  a  flange  coupling  forged  to  its  end  for  the  generator  connection. 
The  guaranteed  efficiency  curve  passes  through  the  following 
points: 

Discharge Full          iff** 

Efficiency  per  cent 80        81        82        80       78       60 

The  t\\o  exciter  units  are  similarly  built.  These  were  required 
to  furnish  700  H.P.  at  450  r.p.m.  under  72  feet  head. 

At  the  intake  the  feeder  pipes  are  9  feet  high  with  semicircular 
ends  of  3-foot  radius,  and  taper  to  a  diameter  of  6  feet  at  the  mouth- 
piece of  the  case.  These  pipes  are  equipped  with  manholes  and  8- 
inch  vent  pipes.  Runners  are  24  J  inches  in  diameter,  the  shaft  5^ 
inches  in  diameter,  and  the  draft  head  is  21  feet  2  inches.  The 
draft  tubes  are  5  feet  6  inches  in  diameter  at  the  case  and  flare  to  a 
width  of  9  feet  10  inches  with  semicircular  ends  of  2  feet  9  inches 
radius. 

For  facility  in  erection,  the  water-wheels  were  mounted  on  a 
long,  heavy  structure  of  I-beams  to  span  the  openings  left  in  the 
masonry  for  the  draft  tubes  extending  from  the  arches  of  power- 
house substructure  to  the  masonry  built  up  outside  the  draft-tube 
clearances.  It  was  proposed  setting  these  with  the  cradles  in 
place,  rigidly  suspending  from  them  the  draft  tubes,  and  then 
filling  in  around  them  with  concrete.  However,  owing  to  delayed 
deliveries  of  the  cradles,  the  draft  tubes  were  loosely  suspended 
from  temporary  beams  braced  to  position  and  concreted  in,  the 
connection  with  the  cradle  fitting  very  well. 


206       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

Regulation  of  this  plant  is  effected  by  Lombard  governors. 
The  generators  are  governed  in  pairs,  and  for  each  pair  a  type 
N  governor  is  provided,  while  both  exciters  are  controlled  by 
one  type  P  governor.  There  are  provided  for  this  installation 
four  4  X  6-inch  triplex  pumps  operated  by  a  belt  from  the  water- 
wheel  shafts.  All  pressure  and  vacuum  tanks  are  placed  in  the 
bearing  tunnel  and  the  entire  system  is  interconnected.  The 
type  N  governors  developing  31,000  foot-pounds  are  guaranteed  to 
completely  open  or  close  the  water-wheel  gates  in  ij  sec.,  while 
the  type  P  governor  will  close  exciter  gates  in  4  sec.,  developing 
6, 700  foot-pounds.  The  larger  governors  are  electrically  controlled 
from  the  switchboard. 

Power-house. — The  generator  turbines  discharge  into  the  tail- 
race  between  piers,  which,  being  spanned  by  full  centred  arches, 
form  the  substructure  of  the  power-house.  These  piers  are  5  feet 
in  width  and  25  feet  between  centres,  except  where  both  exciter 
turbines  discharge  into  the  same  bay,  the  piers  forming  this  one 
being  30  feet  between  centres  and  bridged  by  an  elliptical  arch, 
giving  the  same  rise  as  the  full-centred  arches.  All  piers  and 
also  the  facing  on  exposed  parts  of  the  substructure  were  built 
out  of  very  finely  finished  dimension  stone,  which .  was  quarried 
out  of  locks  built  in  the  early  part  of  the  last  century  by  the  State 
Government  in  an  attempt  at  making  the  river  navigable  past  the 
falls  and  shoals.  By  this  means  and  by  paving  the  bottom  with 
concrete,  these  tail  flumes  were  made  quite  smooth  and  present 
but  little  impediment  to  a  rapid  discharge  of  spent  water.  The 
piers  for  the  three  central  bays  are  carried  in  a  like  manner  down- 
stream from  the  power-house  to  form  the  substructure  for  the 
transformer-house,  but  here  the  span  between  piers  is  not  bridged 
by  an  arch,  except  just  at  the  lower  end,  where  these  arches  carry 
the  outside  wall  and  were  used  largely  for  the  sake  of  maintaining 
a  uniformity  in  the  external  appearance  of  the  structure. 

The  power-house  is  250  feet  long  and  37  feet  wide;  the 
transformer-house  extending  from  this  is  practically,  a  three- 
storied  building,  7 1  feet  in  width  and  85  feet  long.  These  buildings, 


GREAT  FALLS  PLANT  2OJ 

of  fireproof  construction,  are  faced  on  the  outside  with  red  pressed 
brick  and  on  the  inside  with  a  gray  sandlime  brick,  the  body  of 
which  is  granite  dust.  Weepers  were  built  just  back  of  the  brick 
walls  on  the  bulkhead  side  of  the  power-house,  drainage  from  these 
leading  to  the  sump  in  the  power-house.  The  roof  covering  con- 
sists of  tile  resting  directly  on  steel  purlins  supported  by  steel 
trusses.  These  tiles  lay  up  24  X  48  inches,  and  are  built  of  con- 
crete reinforced  by  expanded  metal  and  made  interlocking.  They 
have  a  water-proofing  burned  into  the  exposed  surface.  The 
roof  of  the  transformer-house  was  designed  with  a  wide  overhang 
for  the  protection  of  the  line  openings.  Proper  ventilation  was 
provided  for  by  the  use  of  very  large  windows  with  casement 
side  sash,  which  may  be  widely  opened.  Windows  were  also 
placed  above  the  crane  track  on  the  upstream  side  of  the 
house.  These  windows  are  hinged  on  top,  the  entire  gang  being 
operated  from  two  power  sash-lifting  devices  at  opposite  ends 
of  the  power-house.  By  this  means  it  is  possible  to  close  them 
readily  in  case  of  sudden  shower  when  rain  might  blow  in  on  the 
electrical  machinery.  Two  20-inch  ventilators  were  placed  in  the 
roof  over  each  bay,  and  a  48-inch  slat  ventilator  was  built  into  each 
end  of  the  house.  In  both  ends  of  the  house  are  placed  steel  roll- 
ing doors  with  a  clear  opening  of  16  X  nj  feet. 

A  conduit  for  the  accommodation  of  wires  and  pipe  extends 
along  the  downstream  side  of  the  power-house,  the  top  forming 
a  platform  3  feet  9  inches  above  the  floor  line.  This  platform 
widens  on  a  circular  arch  in  the  centre  of  the  house,  opposite  the 
exciter,  forming  a  dais  for  the  mounting  of  switchboard  and  in- 
strument posts.  A  hand-operated  travelling  crane  runs  from  one 
end  to  the  other  of  the  power-house.  This  has  a  capacity  of  25 
tons,  and  is  equipped  with  a  drum  on  which  is  wound  the  plough- 
steel  hoisting  rope.  The  girders  are  built  of  reinforced  I-beams, 
and  on  the  lower  flange  of  one  of  these  operates  a  5-ton  auxiliary 
trolley  with  triplex  block.  In  the  tunnel  a  5-ton  trolley  is  suspended 
from  the  crown  of  the  arch  on  an  I-beam  track  for  the  handling 
of  wheel  and  bearing  parts. 


208       DEVELOPMENT   AND   DISTRIBUTION  OF   WATER   POWER 

The  transformer-house,  as  already  stated,  is  a  two-storied  struct- 
ure, the  conduit  floor  or  basement  of  which  is  practically  on  a  level 
with  the  bottom  of  the  cable  conduit  in  the  power-house.  The 
skeleton  of  this  floor  consists  of  I-beams  spanning  the  opening  be- 
tween piers,  the  space  between  these  beams  being  spanned  by  con- 
crete arches  with  a  concrete  covering  protecting  the  lower  flanges 
of  the  beams.  The  piers  were  carried  full  width  through  this  floor. 
The  floors  of  the  first  and  second  floor  are  similarly  constructed 
except  that  curved  corrugated  steel  sheets  were  supported  on  the 
lower  flanges  of  the  I-beams,  and  on  these  was  placed  the  concrete. 
The  first  floor  is  on  a  level  with  the  switchboard  platform.  It  is 
divided  into  rooms  for  housing  transformers  over  both  side  bays 
and  extending  the  full  length  of  the  house,  while  that  portion  lying 
above  the  piers  of  the  central  bay  forms  a  room  for  low-tension 
switching  apparatus.  Immediately  back  of  the  switch-room  and 
overlooking  the  tail-race  is  an  office  for  the  operators.  From  the 
power-house,  entrance  is  gained  to  those  rooms  in  which  the  trans- 
formers are  placed  through  arches  protected  by  rolling  steel  fire 
doors  with  fusible  links.  A  similar  door  divides  these  rooms  into 
two  separate  compartments, .  so"  that  any  one  bank  of  transformers 
will  be  automatically  isolated  from  the  others  in  case  of  fire.  The 
second  floor  has  no  partitions  in  it  whatever,  forming  thus  a  room 
of  such  size  as  to  contain  all  the  high-tension  apparatus  with  a 
generous  allowance  for  clearance  between  leads.  All  apparatus 
is  taken  up  through  trap  doors  located  above  the  tracks  for  the 
transformer  transfer  carriage,  thus  making  their  handling  a  simple 
matter.  A  36-inch  ventilator  in  the  roof  will  insure  against  ex- 
cessive temperatures  in  this  room. 

THE  HYDRO-ELECTRIC  DEVELOPMENT  AT  TRENTON 

FALLS,  N.  Y. 

Abstracted  jrom  The  Electrical  World  of  May  19  1906. 

THE  waters  of  the  Canada  Lakes  in  the  Adirondacks  of  New 
York  State  find  their  way  to  the  Mohawk  River  through  two  streams 


TRENTON  FALLS  PLANT  209 

known  as  the  East  and  West  Canada  Creeks.  The  former  empties 
into  the  Mohawk  at  East  Creek  and  the  latter  at  Herkimer.  The 
West  Canada  Creek  is  the  larger,  and  near  the  village  of  Trenton 
Falls  it  has  a  descent  of  nearly  300  feet  in  less  than  a  mile.  It  is 
at  this  place  that  the  8,000  H.P.  hydro-electric  station  of  the  Utica 
Gas  and  Electric  Company  is  located. 

The  Dam. — The  dam  is  a  concrete  structure  of  the  gravity 
type,  300  feet  long  and  60  feet  high,  built  across  the  Creek  on  the 
arc  of  a  circle  having  a  radius  of  800  feet,  at  a  point  about  three- 
quarters  of  a  mile  distant  from  the  power-house. 

Eight  6o-inch  cast-iron  pipes  are  built  into  the  dam  near  the 
bottom,  two  of  wrhich  supply  the  pipe  line  feeding  the  turbines 
now  installed,  two  for  the  supply  of  a  second  pipe  line  when 
the  power-house  is  extended,  and  four  to  assist  the  waste  weirs 
in  carrying  off  the  excess  water  in  times  of  extreme  floods.  All 
of  the  6o-inch  pipes  are  equipped  with  cast-iron  sluice-gates  having 
bronze  guides  and  are  operated  from  the  top  of  the  dam. 

The  flood-water  weirs  above-mentioned  are  two  in  number, 
one  being  built  at  right  angles  to  the  dam  and  close  by  it  on  a 
rock  shelf  on  the  east  bank  of  the  stream,  the  other  forming  a 
part  of  the  dam  proper.  The  first  weir  or  spillway  mentioned  is 
1 60  feet  long,  the  crest  being  9  feet  lower  than  the  top  of  the  coping 
on  the  dam.  The  second  weir  is  100  feet  long  and  its  crest  is  two 
feet  higher  than  the  crest  of  the  former. 

By  this  construction,  the  waste  of  flood  water  in  the  reservoir 
will  flow  over  the  spillway  first  mentioned  through  a  rock  cut 
around  the  dam  to  the  creek  below  until  the  water  flowing  over 
it  is  two  feet  in  depth,  when  the  spillway  on  the  dam  will  come  into 
action  and  both  weirs  will  then  carry  the  waste  water.  The  first 
weir  mentioned  can  be  provided  with  flash-boards,  so  that  the  level 
of  the  water  in  the  reservoir  can  be  raised  two  feet  during  the  dry 
season. 

Both  the  dam  and  the  weir  on  the  dam  are  capped  with  heavy 
stone  coping  securely  held  by  dowel  pins,  while  substantial  stone 
wing  walls  are  constructed  on  the  downstream  face  of  the  dam 


210       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

to  confine  the  flood  water  within  the  limits  of  the  spillway  and 
thereby  protect  the  face  of  the  dam  from  injury  due  to  debris, 
etc.,  in  time  of  floods. 

The  Pipe  Line. — The  conduit  which  conveys  the  water  from 


FIG.  104. — SECTION  THROUGH  BULKHEAD. 

the  reservoir  to  the  turbines  in  the  power-house  is  84  inches  in 
diameter  and  about  3,700  feet  long.  It  is  connected  to  the  two 
westerly  6o-inch  pipes  in  the  dam  by  means  of  a  60  X  60  X  84-inch 
cast-iron  Y  piece  and  two  6o-inch  gate  valves  enclosed  in  a  gate- 
house, the  latter  being  used  to  control  the  flow  of  water  in  the  pipe 
line. 


TRENTON  FALLS  PLANT 


211 


The  long  pipe  is  composed  of  wooden- 
stave  and  steel-plate  pipe,  the  major  por- 
tion of  its  length  being  constructed  of 
Texas  pine  staves  securely  held  in  posi- 
tion by  round-iron  bands,  and  joined  to 
the  steel  pipe  2,900  feet  from  the  dam. 

Twenty  wooden  staves,  each  2-j*  inches 
thick,  sawed  on  radial  lines,  are  used  in 
forming  the  circumference  of  the  84-inch 
diameter  circle,  the  lumber  being  the  best 
of  its  kind  that  could  be  obtained. 

The  steel  pipe,  which  is  about  800 
feet  long,  is  built  of  plate  van-ing  from  f 
to  £  inch  in  thickness,  and  thoroughly 
coated  inside  and  out  at  the  mill  with  hot 
asphalt  pitch.  All  connections  of  plate 
are  made  with  lapped  joints,  the  cir- 
cumferential seams  being  single  riveted, 
while  the  longitudinal  seams  are  double- 
riveted.  All  pipe  constructed  of  J-inch 
material  is  stiffened  by  means  of  angle 
irons. 

The  wooden-stave  pipe  is  built  on  a 
light  descending  grade,  and  it  winds  in 
and  out  along  the  west  bank  of  the  creek 
throughout  its  entire  length.  After  its 
junction  with  the  steel  pipe,  the  grade 
becomes  much  greater  and  the  pipe  con- 
tinues in  a  straight  line  for  several  hun- 
dred feet  to  a  standpipe  84  inches  in  di- 
ameter and  about  200  feet  in  height, 
which  is  built  into  the  supply  conduit  to 
relieve  any  pressure  in  the  line  caused  by 
extreme  load  conditions.  This  standpipe, 
which  is  covered  with  shingled  casing 


:  \ 


\ 


V 


212       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 


having  a  well- shaped  cu- 
pola at  the  top,  •  is  20  feet 
higher  than  the  dam. 

Just  after  passing  the 
standpipe,  the  penstock 
descends  along  the  cliff  at 
a  sharp  angle  to  a  reservoir 
near  the  power-house,  125 
feet  below  the  top  of  the 
bank.  The  reservoir  is 
anchored  on  concrete 
foundations  just  outside 
the  west  wall  of  the  power- 
house. It  is  provided  with 
four  48-inch  outlets,  each 
of  which  delivers  water  to 
a  turbine  wheel  under  a 
head  of  266  feet.  The 
flow  of  water  to  each  tur- 
bine is  controlled  by  a  48- 
inch  gate  valve,  the  ar- 
rangement being  such  that 
any  or  all  valves  can  be 
operated  simultaneously 
by  hand,  or  by  power  fur- 
nished by  a  Pelton  water- 
wheel. 

The  penstocks  to  the 
turbines,  the  pipe  line,  and 
receiver  are  all  equipped 
with  valves  to  assist  in  re- 
lieving any  excess  pressure 
which  might  come  on 
them,  and  the  main  pipe 
line  is  provided  with  a 


TRENTON  FALLS  PLANT  213 

number  of  air  inlet  pipes  to  allow  for  the  escape  or  intake  of  air 
when  the  line  is  being  filled  or  emptied. 

Hydraulic  and  Electrical  Machinery. — The  turbine  units  are 
six  in  number,  four  driving  the  large  generators  and  two  furnishing 
power  to  the  exciter  dynamos.  The  former  units  are  of  a  Four- 
neyron  or  outflow  type,  the  water  from  the  wheel  runners  dis- 
charging into  a  draft  tube.  They  have  vertical  shafts,  hydraul- 
ically  operated  governors,  and  are  .direct-connected  to  the 
generators.  They  have  a  rated  capacity  of  2,000  H.P.  at  full 
gate  opening  when  working  under  264-feet  head. 

The  exciter  turbines,  which  are  of  the  Girard  type,  develop 
100  H.P.  at  full  gate  opening  when  operating  under  the  above- 
mentioned  head.  They  also  have  vertical  shafts,  direct-connected 
to  the  dynamos,  the  speed  regulation  being  under  hand  control. 
The  supply  pipes  of  each  exciter  turbine,  which  are  12  inches  in 
diameter,  are  attached  to  the  penstock  of  the  units  nearest  them, 
the  flow  of  water  being  controlled  by  a  gate  valve  operated  by 
hand  power  only. 

The  main  generators  are  alternators  of  the  internal  revolving- 
field  type,  producing  three-phase  current  at  2,300  volts,  and  60 
cycles  whei  the  field  is  rotating  at  300  r.p.m.  The  exciter  dynamos 
are  i25-volt  machines  and  revolve  normally  at  750  r.p.m. 

The  switchboard  is  of  the  usual  type,  having  a  marble  panel 
for  each  of  the  large  units  and  one, panel  for  the  two  exciter  units. 
It  also  has  separate  high-  and  low-tension  feeder  panels.  The 
potential,  of  the  current  leaving  the  low- tension  feeder  panel,  is 
stepped  up  to  23,000  volts  by  air-cooled  transformers,  from  which 
the  current  passes  to  the  high-tension  feeder  panel,  thence  out  of 
the  building  through  the  lightning  arresters  located  in  a  separate 
building  near  the  power-house,  and  finally  along  the  transmission 
line  to  the  substation  in  Utica,  twelve  miles  away. 

The  Power-house. — The  power-house,  which  is  situated  in  a 
rocky  gorge  slightly  more  than  100  feet  in  width  and  varying  from 
125  to  150  feet  in  depth,  is  a  well-appointed  building  in  all  respects. 
It  is  32  feet  wide  and  128  feet  long  inside,  and  around  the  skeleton 


214       DEVELOPMENT   AND   DISTRIBUTION  OF   WATER   POWER 

steel  framework  are  built  walls  of  Gouverneur  marble,  while  the 
interior  is  trimmed  with  white  and  brown  enamel  brick  to  the  win- 
dow sills,  and  above  this  point  with  cream  pressed  brick  to  the  roof. 
It  is  furnished  with  a  lo-ton  travelling  crane  for  convenience  in 


^ 

FIG.  107. — CROSS-SECTION  OF  POWER-HOUSE. 

handling  any  part  of  the  hydraulic  or  electrical  machinery.  A 
view  of  the  interior  of  the  power-house  is  shown.  The  turbines 
are  all  below  the  granolithic  floor,  in  separate  wheel  pits. 

One  important  feature  of  the  plant  is  there  is  no  trouble  from 


MC CALL  FERRY  PLANT  215 

anchor  ice,  due  to  two  precautions  which  were  taken  when  the 
dam  was  built.  First,  the  pipe  line  enters  the  dam  40  feet  below 
the  surface  of  the  water,  and  anchor  ice  does  not  sink  to  the  level 
of  the  pipes.  Second,  the  crest  of  the  spillway  which  carries  sur- 
plus water  around  the  ends  of  the  dam  is  2  feet  lower  than  the 
spillway  on  the  dam,  and  a  strong  current  is  thus  established  which 
carries  the  anchor  ice  around  the  end  of  the  dam,  and  far  away 
from  the  pipe-line  intake,  which  is  on  the  opposite  side  of  the  stream. 

At  Utica  there  are  two  modern  direct-connected  steam  stations, 
with  a  total  capacity  of  8,000  H.P.,  which  can  be  started  at  once  in 
case  of  interruption  of  the  transmission  lines  from  Trenton  Falls. 
The  last  steam  unit,  which  was  installed  last  fall,  is  a  3,000  H.P. 
steam  turbine,  and  generator  of  same  capacity. 

Extensions. — The  company  proposes  to  add  8,000  H.P.  to  its 
Trenton  Falls  station,  bringing  its  capacity  up  to  16,000  H.P., 
and  also  develop  its  water  power  at  Prospect,  about  one  mile  above 
Trenton  Falls  dam.  At  Prospect  a  plant  having  a  capacity  of 
6,500  H.P.  will  be  built,  and  at  Enos  on  the  Black  River,  nine  miles 
from  Prospect,  the  company  will  build  a  station  having  a  capacity 
of  3,000  H.P.;  thus  the  company  will  possess  a  grand  total  of 
25,500  H.P.  in  hydro-electric  generators. 


THE  HYDRO-ELECTRIC  PLANT  OF  THE  McCALL 
FERRY  POWER  COMPANY. 

Abstracted  from  The  Engineering  Record  of  September  21,  1907. 

THERE  is  now  under  construction  at  McCall  Ferry,  Pa.,  a  hydro- 
electric plant  having  many  unusual  features  in  both  design  and 
methods  of  construction.  It  is  on  the  Susquehanna  River  about 
25  miles  from  Chesapeake  Bay. 

Hydraulic  Conditions. — The  Susquehanna  River  has  a  drain- 
age area  of  27,400  square  miles,  the  larger  part  lying  in  Penn- 
sylvania. Its  watershed  includes  the  steep  slopes  of  the  Allegheny 
Mountains,  which  cause  sudden  rises  of  rather  frequent  occurrence. 


2l6       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

The  river  occupies  a  deep  valley,  and  for  125  miles  above  its  mouth 
has  an  average  slope  of  3 \  feet  per  mile,  the  fall  at  McCall  Ferry 
being  8  feet  per  mile.  The  conditions  on  which  the  design  of  the 
plant  is  based  have  been  studied  at  Harrisburg  since  1890  and  at 
McCall  Ferry  since  1902.  The  records  thus  obtained  show  that 
with  the  adopted  head  of  about  55  feet  the  flow  of  the  river  assisted 
by  an  adequate  storage  capacity  can  be  depended  upon  for  the  con- 
tinuous development  of  100,000  H.P.  The  storage  will  be  se- 
cured by  a  lake  6  miles  long  and  4,000  feet  wide,  formed  by  the 
dam.  The  discharge  necessary  to  develop  the  normal  rating  of 
the  plant  on  a  1 2-hour  load  is  10,000  cubic  feet  per  second,  corre- 
sponding to  an  average  run-off  on  the  catchment  area  of  0.47  cubic 
foot  per  second  per  square  mile,  the  drainage  area  above  McCall 
Ferry  being  26,766  square  miles.  The  discharge  as  peak  load  will 
be  2 7,000  cubic  feet  per  second.  The  flood  flow  considered  in  mak- 
ing the  plans  was  about  671,000  cubic  feet  per  second;  the  record 
of  the  highest  flood,  that  of  June,  1889,  corresponding  to  an  average 
run-off  on  the  drainage  area  of  about  25  cubic  feet  per  second  per 
square  mile.  The  floods  come  with  great  rapidity,  the  flow 
in  the  river  frequently  jumping  from  30,000  to  100,000  cubic 
feet  per  second  or  over.  The  necessity  of  providing  carefully 
for  these  conditions  is  further  emphasized  by  the  large  amount 
of  ice  carried  toward  the  end  of  the  winter,  much  of  it  in  large, 
thick  cakes. 

Dam. — The  plant  and  dam  are  built  at  a  point  where  the  river 
is  about  2,600  feet  wide  and  divided  into  two  channels  by  Fry 
Island.  The  east  or  Lancaster  channel  is  about  900  feet  wide, 
and  the  west  or  York  channel  about  1,200  feet,  and  the  island  about 
500  feet.  The  stream  is  only  400  feet  wide  a  short  distance  above 
the  dam,  but  the  depth  and  swiftness  of  the  current  forbade  con- 
struction there.  The  present  site  offers  a  ready  means  of  handling 
the  flow  during  construction  by  reason  of  the  two  channels.  Above 
and  below  McCall  Ferry  the  river  is  dotted  with  small  islands  and 
crossed  by  ledges,  on  one  of  which  the  dam  rests.  The  water  a 
short  distance  above  and  below  it  is  very  deep.  Another  such 


MCCALL  FERRY  PLANT 


217 


ledge  crosses  the  river  at  Cully's  Falls,  and  a  channel  had  to  be 
cut  through  it  for  the  tail-race.  The  rock,  though  hard,  is  con- 
siderably eroded  and  fissured. 

On  account  of  the  floods,  the  dam  has  been  constructed  as  a 
spillway  throughout  its  entire  length  of  2,350  feet.  The  dam 
extends  only  600  feet  across  the  Lancaster  channel,  the  remainder 
of  the  channel  being  spanned  by  the  power-house.  Its  crest  is 
45  to  50  feet  above  the  average  summer  water  level.  The  section 


'  —  *ua  »»«'^  ^i 

rniiff"^ 

Engmuriny  Record 

FIG.   108.  —  SECTION  OF  DAM. 


has  been  calculated  for  a  head  of  17  J  feet,  above  the  crest  corre- 
sponding to  a  flow  of  304.7  cubic  feet  per  second  per  linear  foot  of 
the  dam,  a  quantity  equal  to  the  maximum  recorded  flow  of  the 
river.  The  section  was  calculated  on  the  assumption  that  the 
weight  of  the  masonry  was  135  pounds  per  cubic  foot,  and  the  weight 
of  the  falling  water  over  the  dam  and  the  pressure  of  the  water  on 
the  apron  were  neglected.  The  base  of  the  dam  is  uniformly 
65  feet  wide,  below  a  point  51  feet  down  from  the  crest.  Where 
the  dam  crosses  the  island,  the  ledge  rises  to  within  41  feet  of  the 
crest,  necessitating  a  change  in  the  section,  which  was  made  by 
retaining  for  the  lower  part  of  the  apron  the  same  curve  as  was 


2l8       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

used  elsewhere,  the  only  difference  in  the  two  sections  being  in  the 
length  of  this  lower  curve  of  the  apron.  The  front  face  is  vertical. 

The  dam  is  1:3:5  Portland  cement  concrete  with  pudding 
stones  up  to  i  cubic  yard  in  size.  The  sand  is  coarse  and  very 
clean,  secured  from  a  bank  at  Charlestown,  Md.  The  stone  is  a  very 
hard  trap,  weighing  193  pounds  per  cubic  foot,  used  without  screen- 
ing, and  contains  pieces  running  up  to  7  inches  in  length.  The 
pudding  stones  are  of  the  same  rock,  which  is  obtained  at 
a  quarry  operated  by  the  company  at  Conowingo,  Md.  These 
stones,  forming  20  per  cent  of  the  total  yarcfege,  are  placed  not 
closer  together  than  8  inches  and  2  feet  back  from,  the  surface 
of  the  concrete.  The  amount  of  material  in  the  dam  is  174,000 
cubic  yards. 

Power-house. — The  power-house  occupies  the  eastern  part  of 
the  east  or  Lancaster  channel,  and  stands  at  an  angle  of  forty-two 
degrees  with  the  face  of  the  main  dam.  In  front  of  it  is  a  forebay, 
where  the  racks  and  screens  are  located,  and  the  entrances  to  the 
chutes  for  disposing  of  any  ice  which  gets  into  the  enclosure.  The 
conduits  leading  to  the  turbines  start  immediately  back  of  the  in- 
clined racks.  They  are  built  entirely  of  concrete,  no  steel  being 
used  either  for  reinforcing  or  for  the  intakes  or  draft  tubes.  The  ten 
turbines  are  beneath  the  power-house  floor,  five  on  each  side  of  the 
two  exciters  in  the  centre  of  the  building.  South  of  the  power- 
house is  the  transformer-house,  carried  by  arches  spanning  the 
draft-tube  outlets  in  the  tail-race. 

The  front  wall  of  the  forebay  is  carried  on  u  arches,  the 
crowns  of  which  are  6  feet  below  the  crest  of  the  dam,  and  i  foot 
below  the  low-water  level,  so  that  they  will  always  be  submerged. 
Back  of  the  arches  and  carried  on  inclined  piers  are  the  screens, 
and  back  of  them  are  the  gates  closing  the  intakes  to  the  turbines. 
The  screens  are  built  in  panels  10  feet  wide  and  n  feet  high,  four 
tiers  to  a  unit.  •  They  have  frames  of  lo-inch  channels,  supporting 
the  screen-bars,  which  are  7-16  X  4j  inches,  with  2-inch  spaces 
between  them.  Instead  of  using  gas-pipe  separators,  as  is  general- 
ly done,  the  bars  are  kept  apart  by  plates  f  inch  thick,  which 


MCCALL  FERRY  PLANT 


219 


220       DEVELOPMENT   AND   DISTRIBUTION  OF  WATER   POWER 

have  notches  cut  in  them  of  the  thickness  of  the  bars.  The  strips 
of  metal  between  the  notches  are  bent  over  the  rods  on  which  the 
bars  are  hung,  thus  holding  the  latter  apart.  The  frames  slide 
in  cast-iron  seats  bolted  to  the  noses  of  the  inclined  piers.  This  ar- 
rangement allows  the  screens  to  be  withdrawn  for  repairs  and  clean- 
ing by  merely  catching  them  with  a  line  from  the  crane,  and  pull- 
ing them  out.  Within  the  forebay  are  two  chutes  for  disposing  of 
any  ice  that  may  get  by  the  exterior  ice  protection.  One  of  these 
chutes  6  feet  square  is  located  between  the  two  exciters  at  the  centre 
of  the  power-house,  and  the  other  measuring  8  X  10  feet  is  at  the 
east  end  of  the  forebay. 

The  gates  closing  the  intake  conduits  are  16  feet  high  and  6 
feet  wide,  and  are  raised  and  lowered  by  the  large  travelling  crane 
in  the  screen  and  gate-room.  An  auxiliary  gate,  also  lowered  and 
raised  by  the  crane,  is  cut  into  the  main  gate,  and  can  be  opened  so 
as  to  equalize  the  pressure  in  the  forebay  and  the  intake  conduits. 

The  intake  conduits  for  the  main  units  start  in  three  openings 
separated  by  piers  each  6  feet  wide  and  16  feet  high.  Eight  feet 
back  from  the  gates  these  three  passages  merge  into  one  which  is 
15  feet  wide,  and  for  a  short  distance  13  feet  high,  expanding  where 
the  conduit  forms  the  turbine  chamber,  to  a  height  of  33  feet.  There 
are  two  draft  tubes,  one  leading  from  each  wheel  of  the  unit. 
These  draft  tubes  join  about  20  feet  from  the  unit,  but  are  here 
divided  by  a  vertical  wall,  the  discharge  outlet  into  the  tail-race  of 
each  unit  being  composed  of  two  passages,  each  13  feet  wide  and 
15  feet  high.  This  arrangement  of  the  draft  tubes,  since  they  are 
constructed  of  solid  concrete,  necessitated  very  complicated  form- 
work,"  especially  since  it  was  necessary  to  have  easily  curving 
surfaces  which  would  offer  little  or  no  resistance  to  the  flow  of 
water.  The  exciters  are  located  in  the  centre  of  the  power-house 
with  five  main  units  on  each  side  of  them.  The  intake  conduits 
and  draft  tubes  for  them  are  6  feet  square  in  section. 

Each  turbine  is  set  in  the  concrete  chamber  without  the  usual 
steel  or  iron  casing.  Each  chamber  can  be  closed  independently 
of  all  the  others,  and  after  being  closed  by  the  gates  in  front  of  the 


MCCALL  FERRY  PLANT 


221 


intake  conduits  and  the  stop-logs  at  the  ends  of  the  draft  tubes,  can  be 
drained  through  outlets  leading  to  pumps  installed  for  that  purpose. 


Below  the  power-house  floor  runs  a  chamber  parallel  to  the 
length  of  the  power-house  in  which  will  be  installed  the  pumps  for 


222       DEVELOPMENT   AND   DISTRIBUTION  OF   WATER   POWER 

draining  the  wheel  chambers  and  the  turbine-driven  oil  pumps  for 
supplying  the  thrust  bearings  with  oil. 

The  turbines  are  of  the  vertical  shaft,  inward  and  downward 
flow,  Francis  type.  There  are  10  main  units  each  capable  of 
developing  13,500  H.P.  under  a  head  of  53  feet  with  the  gates  open 
80  per  cent  at  94  r.p.m.  Each  turbine  when  run  at  its  rated  load 
will  take  about  2,700  cubic  feet  of  water  per  second.  Each  tur- 
bine has  two  separate  wheels  mounted  on  the  same  shaft,  the  latter 
being  of  forged  steel,  20  inches  in  diameter.  The  upper  wheel 
discharges  through  a  steel  casing  leading  to  the  draft  tube  while 
the  lower  wheel  is  set  imrrediately  over  the  draft- tube  pit,  and  dis- 
charges into  it  without  the  medium  of  a  casing.  The  wheels  are 
about  10  feet  in  diameter. 

The  weight  of  all  the  moving  parts  of  both  generator  and  tur- 
bine is  carried  on  a  thrust  bearing  which  is  supplied  with  oil  from 
pumps  driven  by  small  turbines.  Separating  the  oil  pumps  in  this 
manner  from  the  main  units  allows  the  oil  in  the  thrust  bearing  to 
be  put  under  pressure  before  the  unit  is  started.  The  thrust  bear- 
ing, which  carries  a  total  weight  of  335,000  pounds,  is  supported 
by  a  lens-shaped  casting  set  into  the  concrete.  The  exciters 
have  a  capacity  of  1,000  H.P.  and  are  of  the  same  general  type  as 
the  main  units. 

Ice  Protection. — The  large  amount  of  ice  which  has  to  be  dis- 
posed of  and  its  long  continuance  each  winter  have  necessitated 
special  precautions  for  protecting  the  plant  and  turbines.  It  is 
aimed  to  keep  the  entire  enclosed  forebay  free  from  ice,  and  to 
accomplish  this  an  outer  forebay  is  provided  and  separated  from 
the  main  river  by  a  series  of  submerged  arches  and  timber  cribs, 
which  form  racks  holding  in  place  floating  booms.  This  ice  pro- 
tection is  630  feet  long,  and  stretches  from  the  point  where  the 
main  dam  and  the  power-house  join  to  a  ramp  300  feet  long  built 
out  from  the  shore.  The  concrete  ice  protection  consists  of  3  sub- 
merged arches  each  having  a  span  of  68  feet  with  8-feet  piers  be- 
tween them.  The  crowns  of  the  arches  are  2  feet  below  the  esti- 
mated low-water  elevation  so  that  the  arches  are  always  submerged, 


MCCALL  FERRY  PLANT  223 

the  ice  and  floating  debris  being  thus  stopped  and  floated  toward 
the  dam,  where  a  special  runway  for  this  purpose  has  been  con- 
structed between  the  main  dam  and  the  power-house.  The  top 
of  this  concrete  structure  rises  to  a  height  of  22  feet  above  the  crest 
of  the  dam  and  4 J  feet  above  the  high- water  elevation.  The  top 
is  6  feet  wide  and  the  back  face  has  a  batter  of  4  inches  to  the  foot, 
the  piers  at  rock  foundation  being  30  feet.  long.  The  space  be- 
tween the  concrete  structure  and  the  ramp  is  occupied  by  four 
timber,  rock-filled  cribs,  spaced  104  feet  apart  and  supporting  float- 
ing booms.  These  cribs  are  24  feet  wide  and  16  feet  long  on  top, 
the  length  increasing  with  the  depth,  being  64  feet  at  the  foundation. 
The  floating  stop-logs  between  the  cribs  are  made  of  three  layers 
of  six  10  X  i2-inch  timbers  each.  They  are  bolted  together  with 
spaces  between  them  so  as  to  make  the  boom  7  feet  8  inches  wide 
and  3  feet  thick.  The  boom  slides  in  recesses  in  the  timber  cribs, 
rising  and  falling  with  the  stage  of  the  water  above  the  dam. 
The  direction  of  the  ice  protection  is  parallel  to  the  flow  of  the  river 
so  that  the  flow  will  assist  in  carrying  the  ice  and  debris  toward 
the  main  dam  and  over  the  runway. 

In  addition  to  this  ice  protection,  a  spillway  has  been  provided 
between  the  powrer-house  and  the  shore  for  disposing  of  any  ice 
which  forms  in  the  forebay  or  finds  its  way  into  it.  This  spillway 
40  feet  wide  has  the  same  elevation  as  the  crest  of  the  main  dam. 
Separating  it  from  the  power-house  and  protecting  the  latter  from 
the  ice  passing  to  the  spillway  is  a  wall  8  feet  thick  reaching  above 
the  high-water  elevation.  This  spillway  cuts  off  the  power-house 
from  the  shore,  and  access  between  them  is  had  by  a  bridge  5  feet 
wide,  and  by  a  tunnel  14  feet  wide  and  16  feet  high  running  through 
it.  The  tunnel  is  laid  with  a  standard-gauge  track  wrhich  extends 
55  feet  inside  the  power-house,  allowing  the  machinery  to  be  handled 
directly  from  the  cars  by  the  power-house  cranes. 

Tail-race. — The  tail-race,  3,000  feet  long,  is  nothing  more  than 
the  former  bed  of  the  Lancaster  channel,  lying  between  the  east 
bank  of  the  river  and  the  chain  of  islands  south  of  Fry  Island. 
This  channel  presents  a  very  curious  formation.  The  bed  is  of 


224       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

solid  gneiss,  with  benches  on  either  side  submerged  at  the  original 
condition  of  the  river  from  7  to  10  feet,  and  having  between  them 
a  channel  about  100  feet  wide  and  from  80  to  90  feet  deep,  with 
vertical  walls.  This  unusual  depth  continues  until  near  the  point 
where  the  tail-race  flows  into  the  main  channel  of  the  river.  A 
ledge  of  rock  is  here  encountered  through  which  a  channel  i  ,000  feet 
long  and  varying  in  width  from  150  to  300  feet  is  blasted.  In 
order  to  prevent  the  river  from  flooding  the  tail-race  by  flowing 
through  the  openings  between  the  islands  which  separate  the 
two  channels,  rock-filled  timber  cribs  are  thrown  across  these 
openings,  and  carried  above  the  highest  level  which  the  water  in 
the  channel  can  reach.  At  the  point  where  the  rock  ledge  ob- 
structs the  channel  near  the  end  of  the  tail-race  a  concrete  weir  is 
built,  with  its  crest  at  the  same  elevation  as  the  top  of  the  draft- 
tube  outlets,  so  as  to  preserve  a  water  seal  for  the  turbines. 

In  order  to  prevent  a  large  volume  of  the  water  which  comes 
over  the  dam  from  finding  its  way  at  once  into  the  tail-race,  and  thus 
raising  the  level  of  the  latter,  a  deflecting  dam  576  feet  long  starts 
at  the  junction  of  the  main  dam  and  the  power-house,  just  opposite 
the  beginning  on  the  upstream  side  of  the  ice  protection,  and  runs 
over  to  Piney  Island,  which  lies  south  of  Fry  Island.  This  dam 
is  built  of  solid  concrete,  using  pudding  stones  and  the  propor- 
tions which  were  adopted  for  the  main  dam.  Its  crest  is  at  the 
same  level  as  the  power-house  floor,  14  feet  below  the  crest  of 
the  main  spillway.  With  this  dam,  and  the  cribwork  between 
the  islands  below  the  plant,  the  water  coming  over  the  main  dam, 
is  confined  entirely  to  the  western  or  York  channel,  allowing  the 
Lancaster  channel  to  be  used  for  the  tail-race.  The  low- water  level 
in  the  latter  is  about  15  feet  below  the  water  level  in  the  spillway 
channel  immediately  below  the  dam. 

Construction. — Construction  was  first  started  across  the  Lan- 
caster channel,  which  carried  the  greater  volume  of  water  and  in 
which  the  power-house  is  located.  On  account  of  the  rapid  rise 
of  the  river,  and  the  large  discharge  during  high  water,  the  prob- 
lem of  constructing  the  dam  was  a  serious  one.  To  have  provided 


MCCALL  FERRY  PLANT  225 

against  the  maximum  flood  during  construction  would  have  in- 
volved great  expense,  while  any  less  provision  meant  the  occasional 
stoppage  of  the  work,  and  the  probable  loss  or  damage  of  the  con- 
struction equipment  and  the  partially  completed  work.  After  a 
thorough  study  of  all  the  conditions  it  was  decided  to  construct  a 
cofferdam  sufficiently  high  to  prevent  being  overtopped  by  a  flood 
less  than  60,000  cubic  feet  per  second.  Daily  reports  regarding 
the  weather  conditions  on  the  watershed  were  received  from  the 
weather  bureau  at  Harrisburg,  and  when  a  flood  above  60,000  sec. 
feet  was  on  the  way  preparations  were  made  to  meet  it.  Such  a 
case  occurred  on  March  15,  1907,  when  a  flood  of  320,000  cubic  feet 
per  second  swept  over  the  work.  Warning  had  been  received  and 
everything  movable  in  the  path  of  the  water  was  moved  to  a  place 
of  safety,  and  work  carried  on  without  interruption  until  within  an 
hour  of  the  arrival  of  the  flood,  when  the  remaining  equipment 
was  run  to  cover.  The  flood  did  no  damage  to  the  partially  com- 
pleted dam  and  power-house,  but  carried  off  four  standard-gauge 
tracks  laid  with  60  pound  rail  which  were  on  the  construction 
bridge  below  the  dam. 

Cof/erdam. — The  first  step  in  the  actual  work  of  harnessing 
the  river  consisted  in  building  the  cofferdam,  a  rock-filled  timber 
structure  1,000  feet  long  and  about  300  feet  up  the  river  from  the 
site  of  the  dam.  Soundings  had  been  made  across  the  channel 
at  the  places  where  the  cribs  were  to  rest,  and,  where  these  did  not 
give  a  satisfactory  description  of  the  bottom,  divers  were  sent  down 
to  get  more  accurate  information.  The  bottoms  of  the  cribs  were 
then  framed  on  shore  to  fit  the  rock  foundation  on  which  they  were 
to  rest,  and,  after  having  a  few  courses  of  timber  built  upon  them, 
were  launched,  towed  into  position,  and  held  there  by  cables 
anchored  on  shore.  They  were  then  built  up  in  the  usual  manner, 
the  timbers,  which  were  8  X  10  inches,  being  drift-bolted  together 
with  f-inch  drift-bolts,  30  inches  long.  The  materials  were 
conveyed  to  the  cribs  by  means  of  a  cableway  with  a  span  of 
1,200  feet  over  the  site  of  the  cofferdam.  In  addition  to  this 
means  of  conveyance,  a  standard-gauge  track  was  carried  out  and 


226       DEVELOPMENT   AND   DISTRIBUTION  OF   WATER   POWER 

extended  over  each  separate  crib  as  soon  as  completed,  and  on  it 
was  run  a  travelling  stiff -leg  derrick.  Rock  was  placed  in  the  cribs 
to  sink  them  as  the  timber  work  was  carried  up.  The  cribs  were 
1 6  feet  wide  and  varied  in  length,  in  multiples  of  8  feet  from  24  to 
40  feet,  being  built  in  bays  8  feet  square.  The  deepest  crib  was 
about  30  feet  below  the  original  low-water  level. 

The  openings  between  the  cribs  were  closed  with  stop-logs, 
and  in  front  of  them  were  placed  two  rows  of  2 -inch  timber  sheeting 
breaking  joints.  The  careful  placing  of  this  sheeting  is  largely 
responsible  for  the  remarkable  tightness  of  the  cofferdam.  The 
separate  planks  were  driven  to  the  bottom,  rammed  slightly,  and 
on  being  drawn  up  showed  by  the  bruising  of  the  ends  how  they 
were  to  be  cut  to  fit  the  rock  bottom.  After  being  shaped  they 
were  again  put  in  place  and  rammed,  and  withdrawn  a  second  time 
to  determine  whether  further  fitting  was  necessary.  Against  the 
sheeting  was  thrown  the  strippings  from  the  excavations  for  the 
dam  and  power-house,  a  mixture  of  sand  and  loam,  and  on  top 
of  this  a  quantity  of  rip-rap. 

Foundation. — It  was  found  that  the  rock  bottom  for  the  founda- 
tion of  the  power-house  was  of  the  same  hard  gneiss  which  had  been 
examined,  before  the  work  commenced,  on  the  banks  of  the  river 
and  the  islands  near  the  proposed  site.  Near  the  western  end  of 
the  power-house,  however,  the  rock  became  more  dense,  contained 
less  mica,  and  finally  merged  into  a  very  hard  and  dense  trap,  quite 
similar  to  that  quarried  at  Conowingo  and  used  in  the  concrete 
and  for  pudding  stones.  Examination  showed  it  to  be  a  dike  which 
ran  to  Fry  Island  and  then  disappeared.  Both  the  trap  and  gneiss 
were  excellent  foundations  for  the  heavy  structures,  and  test  holes 
drilled  the  whole  length  of  the  work  showed  the  same  high  quality 
of  rock  for  a  depth  of  40  feet  below  the  river-bed.  The  surface  rock 
which  was  considerably  eroded  and  fissured  was  removed,  and  at  the 
shore  end  of  the  power-house  about  50,000  cubic  yards  of  the  solid 
rock  had  to  be  taken  out.  The  surface  of  the  rock  was  then  thor- 
oughly cleaned,  and  a  layer  of  cement  grout  spread  over  it  pre- 
liminary to  placing  the  concrete.  The  amount  placed  at  any  one 


MC CALL  FEPRY  PLANT 


227 


228       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

time  was  governed  by  the  strength  of  the  forms,  very  close  super- 
vision being  given  so  as  to  guard  against  bulging.  The  bond  be- 
tween successive  sections  is  secured  by  embedding  pudding  stones 
in  the  surface  of  the  work  which  is  to  be  left  to  set.  When  the  next 
course  is  added,  the  surface  is  first  thoroughly  swept  with  wire 
brushes,  and  then  washed.  Cement  grout  is  spread  over  the  sur- 
face, and  the  concrete  work  continued. 

Forms. — The  forms  for  the  turbine  intakes,  and  chambers,  and 
draft  tubes  were  quite  complicated,  as  everything  is  built  of  plain 
concrete.  They  were  carefully  designed  and  built  by  experienced 
form  builders.  In  order  to  fashion  the  complicated  curves  on 
many  of  the  forms,  sheet  iron  and  bass  wood  were  used,  the  latter 
being  bent  into  shape  after  being  steamed.  The  forms  were  very 
heavily  braced  and  tied  across  when  possible  by  iron  rods,  as  any 
bulging  or  displacement  would  result  in  altering  the  carefully  de- 
signed water  passages,  and  cause  a  loss  of  head  by  obstructing  or 
changing  the  course  of  the  flowing  water. 

The  forms  for  the  dam  consist  of  structural- steel  bracing  com- 
pletely spanning  the  section  of  the  dam,  and  resting  on  two  shoes, 
one  on  the  upstream  and  one  on  the  downstream  side.  They 
are  placed  10  feet  on  centres,  and  the  spaces  between  them  are  filled 
with  framed  wooden  cradles  bolted  to  the  steel  forms,  and  having 
the  curves  of  the  surface  of  the  dam.  The  steel  forms  consist  of  a 
post  with  a  total  height  of  57  feet  supporting  a  rafter  which  runs 
over  the  apron,  and  rests  on  a  shoe  at  a  horizontal  distance  of  68 
feet  2 1  inches  from  the  shoe  under  the  post.  Beneath  the  inclined 
rafter  is  carried  a  1 2-inch  2o|-pound  channel  having  the  exact 
curve  of  the  apron.  On  the  bottom  of  the  channel  is  a  2 -inch  tim- 
ber, bolted  to  it,  and  having  a  width  of  i  foot  9^  inches.  Bolted  to 
this  strip  are  uprights  3  inches  wide  and  6  inches  high  on  each  side, 
having  bolt  holes  through  them  by  which  the  cradles  are  fastened 
between  the  steel  frames.  The  cradles  are  each  8  feet  2|  inches 
long  and  4  feet  2|  inches  wide,  and  each  one  is  numbered  according 
to  an  erecting  diagram,  for  its  proper  place  on  the  dam.  On  the 
channel  sections  the  dam  is  being  built  in  4o-f eet  piers,  with  4O-feet 


TAYLOR  S  FALLS  PLANT  22Q 

openings  between  them.  For  these  piers  five  of  the  steel  forms 
were  used  and  braced  together  by  diagonals,  and  by  a  large  box 
beam  connecting  the  forms  above  the  crest  of  the  dam.  At  the 
shore  of  Fry  Island,  where  the  section  was  changed,  the  steel  forms 
could  not  be  used  because  of  the  warped  surface  connecting  the  sec- 
tions. Wooden-braced  forms  were  therefore  put  in  place,  and  the 
value  of  the  steel  forms  was  demonstrated  by  the  difficulty  experi- 
enced at  this  point.  The  steel  forms  were  used  on  the  island  section 
by  merely  unbolting  the  rafter  at  the  center  and  allowing  the  two 
parts  to  overlap  and  pass  each  other,  the  lower  part  of  the  apron 
having  the  same  curve  on  both  sections,  thus  obviating  the  necessity 
of  having  two  distinct  sets  of  forms.  The  forms  and  cradles  were 
placed,  removed,  and  transported  along  the  dam  by  the  large  cranes. 
It  was  not  found  necessary  to  provide  any  means  for  holding  the 
forms  down,  as  their  weight  alone  was  sufficient,  but  wires  were 
passed  through  the  dam,  tying  the  vertical  post  and  the  rafter  to- 
gether to  prevent  the  latter  from  bulging.  An  additional  advantage 
of  the  steel  forms  lies  in  the  saving  in  instrument  work,  it  being 
necessary  to  set  only  the  shoes  with  transit  and  level. 


THE  TAYLOR'S  FALLS-MINNEAPOLIS  TRANSMISSION 

SYSTEM. 

Abstracted  from  The  Electrical  World  oj  July  6,  September  7, 
and  October  5,  1907. 

THERE  has  recently  been  put  into  operation  at  Taylor's  Falls, 
on  the  St.  Croix  River,  40  miles  from  Minneapolis,  a  water-power 
plant  of  a  present  capacity  of  10,000  K.W.  and  an  ultimate  capacity 
of  20,000  K.W.  It  has  been  erected  for  the  purpose  of  supplying 
power  to  the  Minneapolis  General  Electric  Company,  which  is  the 
central  station  company  of  Minneapolis.  This  water-power  plant 
and  the  transmission  line  and  distribution  system  connected  with 
it  are  among  the  notable  recent  engineering  works  of  the  country. 
Its  capacity  is  sufficient  to  take  care  of  all  the  present  electric-light 


230       DEVELOPMENT  AND  DISTRIBUTION  OF  WATER  POWER 

and  power  business  in  Minneapolis.     The  purpose  of  this  article  is 
to  describe  the  water-power  development  of  the  falls. 

Hydraulic  Development. — The  St.  Croix  River  is  an  excellent 
stream  for  water-power  purposes,  because  it  is  fed  by  many  lakes 
which  act  as  storage  reservoirs.  The  dam  at  Taylor's  Falls  is  50 
feet  high  and  740  feet  long.  A  much  shorter  dam  would  have  been 
sufficient  to  obstruct  the  flow  of  the  river,  but  this  length  was  given 
to  provide  a  long  spillway  for  flood  waters.  A  map  of  the  dam, 


FIG.   112. — MAP  OF  WORKS  AT  TAYLOR'S  FALLS. 

power  plant,  and  river  in  the  vicinity  of  the  falls  is  shown  in  Fig. 
112.  The  original  course  of  the  stream  is  shown  by  the  dotted 
lines,  the  river  being  naturally  very  narrow  at  this  point. 

The  power  station  is  located  on  what  was  formerly  a  point  of 
land,  excavation  having  been  made  for  the  tail-race.  By  virtue 
of  the  tail-race  excavation  an  effective  head  of  56  feet  is  obtained, 
although  the  dam  is  only  50  feet  high.  The  location  is  almost 
an  ideal  one  for  the  development  of  large  power  and  storage 
capacity  without  excessive  flooding  of  upstream  land.  The  St. 
Croix  River  runs  between  high,  narrow  banks  for  the  entire  n 


TAYLOR'S  FALLS  PLANT  231 

miles  up-stream  influenced  by  this  dam.  The  only  construction 
work  which  had  to  be  done  to  prevent  overflowing  extensive  land 
was  the  building  of  a  concrete  dike  on  the  Minnesota  side  of  the 
river,  as  shown  in  Fig.  112.  Eleven  miles  above  Taylor's  Falls  is 
Never's  Dam,  owned  by  the  same  company  and  maintained  for 
the  purpose  of  storing  water  with  which  to  supply  the  Taylor's 
Falls  power  plant  in  dry  seasons. 

As  seen  by  the  map  (Fig.  112),  provision  has  been  made  for  a 
log  sluice  on  the  Minnesota  side  of  the  river,  entrance  to  which  is 
through  a  bear-trap  dam.  A  log  boom  extends  across  the  river 
so  as  to  divert  logs  to  the  sluice,  and  a  swinging  boom  protecting  the 
sluice  is  also  placed  above  the  bear-trap  dam.  A  fishway  is 
placed  at  one  end  of  the  power  station,  as  indicated. 

The  dam  is  simply  a  piece  of  solid  concrete  construction  resting 
on  bed-rock.  The  rock  used  in  this  construction  was  obtained 
on  the  spot.  In  many  cases  large  chunks  of  trap  rock  were  cleaned, 
dropped  into  place  and  surrounded  by  concrete,  6  inches  on  all 
sides.  The  concrete  used  in  the  dam  was  a  mixture  of  one  part 
cement,  three  of  sand,  and  five  of  crushed  stone  from  trap  rock 
found  on  the  place.  Samples  of  each  carload  of  cement  were  tested 
at  the  construction  office  at  the  falls.  The  first  part  of  the  dam  was 
built  with  openings  in  the  bottom  through  which  the  river  was  di- 
verted by  a  cofferdam  when  the  remaining  portion  of  the  dam  was 
being  built.  The  forebay  is  protected  by  a  drift  boom  located  as 
shown  in  Fig.  112.  Fig.  114  is  a  view  of  the  forebay  showing  the 
ice  and  drift  racks,  which  are  easily  accessible  to  workmen  with 
rakes.  A  crane  has  been  left  in  position  for  the  purpose  of  lifting 
heavy  driftwood  out  of  the  forebay  if  necessary.  The  dam  proper 
extends  clear  through  under  the  power-house,  and  the  power-house 
building  is  erected  on  the  face  of  the  dam.  Fig.  115  shows  a  cross- 
section  of  the  dam  at  the  power-house,  the  power-house  foundation, 
showing  the  position  of  the  intake  pipe,  turbines,  and  draft  tubes. 
The  intake  pipe,  14  feet  in  diameter,  has  an  elbow  leading  into  the 
turbine  casing.  From  the  top  of  this  elbow  a  3-foot  air  vent  pipe 
is  led  off.  Over  the  middle  of  the  turbine  casing  is  an  opening 


232       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

through  which  parts  can  be  hoisted  out  for  replacement  or  repairs. 
As  will  be  seen  from  the  cross- section  drawing  of  the  power-house 


(Fig.  116),  there  is  an  I-beam  on  the  ceiling  of  the  wheel  gallery 
which  is  located  directly  over  this  opening  into  the  turbine  casing. 


TAYLOR'S  FALLS  PLANT  233 

This  I-beam  carries  an  electric  travelling  hoist  which  can  be  run 
over  any  one  of  the  turbines  while  repairs  are  going  on,  and  with 
it  parts  can  be  carried  to  the  end  of  the  power-house.  From  the 
turbine  casing  two  draft  tubes  yj  feet  in  diameter  drop  to  the  tail- 
race. 

Power-Home. — Before  proceeding  to  a  description  of  the  gates, 
gate-operating  machinery,  and  turbines,  the  general  arrangement 
of  the  power  station  will  be  considered  further.  On  the  lower  floor 


FlG.     114. FOREBAY    AND    RACKS. 

is  the  generator-room,  spanned  by  a  25-ton,  3-motor  crane.  On 
the  second  floor  are  the  transformer- rooms  and  switchboard. 
Each  bank  of  three  transformers  is  in  a  separate  fireproof  room 
and  arranged  to  roll  out  onto  the  gallery  under  the  main  crane. 
On  the  same  floor  as  the  transformers,  but  separated  from  them, 
is  the  operating  switchboard  located  so  that  the  attendant  can  see 
from  the  gallery  what  is  going  on  in  the  generator-room.  The 
5o,ooo-volt  leads  from  the  transformers  go  up  through  the  floor  to 
oil  switches  and  then  into  bus  compartments  in  a  cell-room.  From 
the  cell-room  the  5o,ooo-volt  conductors  pass  up  to  oil  switches 
and  from  there  to  the  protective  apparatus  and  out  to  a  steel 
tower,  from  which  a  span  is  made  across  the  river  to  connect  it  to 
the  pole  line  to  Minneapolis. 

In  the  uppermost  story  of  the  power  plant  is  the  motor-operated 
gate-lifting  mechanism. 

Turbines. — There  are  four  turbine  units  each  direct-connected 
to  a  2,5oo-K.W.  generator.  Each  of  these  turbine  units  has  four 


234       DEVELOPMENT   AND    DISTRIBUTION   OF   WATER   POWER 

runners  36  inches  in  diameter  mounted  on  the  same  shaft.  At  277 
r.p.m.  the  turbines  are  rated  at  4,200 H. P.  each  with  55  feet  head; 
at  48  feet  head,  3,400  H.P.;  at  45  feet  head,  3,150!!.?.  The  run- 


m  m  n  P£j  w  PJ 


ELEVATION 


FIG.   115. — ELEVATION  AND  SECTION  OF  POWER-HOUSE. 

ners  are  removable  in  the  manner  described  in  the  general  arrange- 
ment of  the  power-house.  The  penstock  leading  to  each  set  of 
turbines  is  14  feet  in  diameter  and  the  two  draft  tubes  7  feet  in 
diameter,  the  total  effective  head  being  55  feet. 

The  water-wheel  speed  is  regulated  with  Lombard  governors, 
these   governors   controlling   the   gates  with  oil   pressure.     The 


TAYLOR'S  FALLS  PLANT 


235 


oil-pressure  tanks  for  the  four  governors  are  connected  in  mul- 
tiple. The  wheel  units  can  be  started,  stopped,  and  controlled 
from  the  switchboard  by  small  motors  mounted  on  the  governor 
heads  and  so  connected  as  to  raise  or  lower  the  running  speed  of 
the  governor.  These  governors  were  installed  under  a  guaranty 
that  an  instantaneous  variation  of  20  per  cent,  in  the  load  on  the 
generator  should  not  cause  more  than  2  per  cent,  speed  variation, 
and  that  only  for  4  seconds.  In  the  case  of  the  opening  of  a  short- 
circuit  on  the  generators  the  speed  is  guaranteed  not  to  change 
over  12  per  cent,  and  to  return  to  normal  within  7  seconds  or  less. 
The  two  turbines  which  drive  the  exciters  have  each  a  runner 


FIG.  116. — SECTION  OF  POWER-HOUSE. 

1 8  inches  in  diameter.  These  turbines  are  rated  at  200  H.P.  at 
525  r.p.m.  with  55  feet  head.  Besides  being  direct-connected 
to  an  exciter,  one  of  these  turbines  can  be  connected  through  a  fric- 
tion drive  to  a  rotary  fire  pump  for  fire  purposes.  The  friction 
drive  is  of  the  grooved-pulley  type. 

Generators. — There  are  now  installed  four  2,5oo-K.W.,  three- 
phase,  6o-cycle,  2, 300- volt  generators.   The  power-house  has  room 


TAYLOR'S  FALLS  PLANT  237 

for  one  more  generator  of  this  size  at  the  end  now  occupied  by  the 
machine  shop,  and  by  extending  the  building  three  additional  gen- 
erators can  be  installed,  making  a  total  capacity  of  eight  2,5oo-K.W. 
machines,  or  20,000  K.W.  The  generators  are  guaranteed  to  take 
a  load  of  2, 500  K.W.  continuously  and  a  load  of  3,125  K.W.  for  two 
hours  without  exceeding  the  usual  allowable  temperature  rise. 


FIG.   1 1 8. — INTERIOR  OF  POWER-HOUSE,  TAYLOR'S  FALLS. 

Although  their  normal  speed  is  277  r.p.m.,  they  are  calculated  to 
withstand  554  r.p.m.  without  excessive  strain.  If  driven  at  con- 
stant speed  the  drop  in  voltage  between  no  load  and  full  load  with 
constant  field  excitation  is  6  per  cent.  The  field-excitation  current 
is  225  amperes  at  125  volts.  The  efficiency  at  full  load  is  96  per 


238       DEVELOPMENT   AND   DISTRIBUTION  OF   WATER  POWER 

cent.,  at  three-fourths  load  95  per  cent.,  and  at  one-half  load  93  per 
cent.  The  field-puncture  test  is  1,500  volts,  and  the  armature  test 
5,000  volts. 

The  two  water- wheel-driven  exciters  are  100  K.W.,  i25-volt 
machines,  direct-connected  to  the  water-wheels  before  described. 
These  exciters,  which  have  an  overload  capacity  of  150  K.W.  for 
two  hours,  are  compound-wound  with  a  series  winding  sufficient 
to  maintain  constant  voltage  from  no  load  to  full  load;  or,  in 
other  words,  a  flat  characteristic.  Their  effective  voltage  can  be 
varied  by  the  rheostat  between  90  and  130  volts.  The  efficiency 
at  full  load  is  90  per  cent.,  one-fourth  load  80  per  cent.,  and  at 
50  per  cent,  overload  89  per  cent.  In  Fig.  118  is  seen  a  general 
interior  view  of  the  generator-room,  showing  the  machines  just 
described,  one  of  the  exciters,  however,  not  having  been  installed 
when  this  \iew  was  taken.  Room  has  been  provided  for  the  in- 
stallation of  a  loo-K.W.  motor-driven  exciter  between  the  two 
other  exciters  when  the  power-house  is  extended. 

Trans jormer -rooms. — The  transformer- rooms  or  -cells  are  among 
the  most  interesting  features  of  the  plant.  The  doors  opening  into 
these  cells  can  be  seen  at  the  gallery  on  the  right  in  Fig.  118,  above 
each  generator.  There  is  one  bank  of  transformers  for  each 
generator,  and  ordinarily  a  generator  and  its  bank  of  transformers 
are  considered  as  a  unit,  although  provisions  for  separating  them 
are  made  in  the  wiring  scheme  of  the  station,  which  will  be  de- 
scribed later.  A  view  into  one  of  the  transformer  cells  is  shown  in 
Fig.  119.  The  transformer  cells  are  of  solid  concrete  with  a  fire- 
door  opening  onto  the  gallery  in  front.  The  fire-doors  are  held 
open  by  fusible  links  to  allow  the  doors  to  slide  shut  in  case  of  fire. 
The  transformers  are  each  of  900  K.W.  The  primary  voltage  is 
2,300  and  the  secondary  voltage  50,000.  They  are  oil  and  water 
cooled,  the  water  being  piped  from  the  forebay.  The  oil  can  be 
drained  from  the  transformers  by  opening  a  valve  which  is  accessible 
in  the  wheel  gallery  behind  the  transformer  cells;  thus,  in  case  of 
fire  in  a  transformer  case,  the  oil  can  be  drained  off  without  enter- 
ing the  cell,  and  the  cell  can  be  kept  closed.  As  shown  in  Fig.  119, 


TAYLOR'S  FALLS  PLANT  239 

each  transformer  is  mounted  on  a  four-wheeled  truck  and  there  are 
tracks  converging  toward  the  door  so  that  any  one  of  the  transform- 
ers can  be  run  onto  the  gallery,  where  it  can  be  picked  up  by  the 
travelling  crane. 

On  the  top  floor  of  the  building  is  an  electrically  heated  oil- 
treating  tank  4  feet  in  diameter  X  8  feet  long,  in  which  enough 


FIG.  119. — TRANSFORMER  CELL. 

oil  can  be  treated  for  one  transformer.  It  contains  electric  heating 
coils  requiring  a  maximum  of  45  K.W.  When  the  oil  is  heated 
with  these  coils  a  motor-operated  vacuum  pump  8  inches  in  diam- 
eter X  6  inches  stroke  pumps  out  the  steam  that  may  be  formed 
from  any  moisture  in  the  oil.  The  power  station  is  piped  for 
transformer  and  switch  oil. 

Switches  and  Wiring. — Each  generator  is  connected  directly 
to  its  bank  of  step-up  transformers  without  the  intervention  of  any 
oil  switch,  although  there  is  a  set  of  disconnecting  switches  in  the 
leads  of  each  generator  before  they  come  to  the  current  and  poten- 


240       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

tial  transformers.  In  ordinary  operation  generators  are  connected 
in  parallel  by  means  of  the  oil  switches  on  the  50,000- volt  side  of 
the  transformer,  thus  putting  them  in  parallel  on  the  50,000- 
volt  bus-bars.  The' 50,000- volt  bus-bars  are  therefore  the  usual 
operating  bus-bars  of  the  station.  One  set  of  2, 300- volt  bus-bars 
is  operated,  however,  and  branches  from  the  leads  of  each  gen- 
erator are  taken  to  oil  switches,  by  which  each  generator  can  be 
connected  to  the  2, 300- volt  bus-bars.  These  2, 300- volt  bus-bars 
are  ordinarily  intended  for  use  in  supplying  2, 300- volt  current 
in  the  vicinity  of  the  power  plant.  They  can  also  be  made  a  means 
of  connecting  a  generator  to  a  bank  of  transformers  other  than  the 
one  to  which  it  is  normally  connected,  as  might  be  necessary  in 
case  of  the  break-down  of  a  generator  and  a  bank  of  transformers 
connected  to  another  generator.  The  wiring  scheme  is  designed 
for  the  completed  power  station;  but  not  all  of  the  circuits  have 
as  yet  been  installed.  There  is  now  a  single  set  of  50,000- volt  bus- 
bars. Provision  is  made  for  a  double  set  of  5o,ooo-volt  bus-bars 
and  an  extra  set  of  switches  whereby  each  generator  can  be  con- 
nected with  either  set  of  bus-bars.  Static  dischargers  are  con- 
nected between  the  generators  and  transformers,  being  located 
in  the  transformer  cell-rooms.  While  provision  is  made  for  two 
outgoing  5o,oco-volt  transmission  lines,  at  present  there  is  only 
one  such  line.  There  is  an  oil  switch  between  the  5o,ooo-volt  bus- 
bars and  the  line. 

The  2, 300- volt  leads  from  each  generator  are  carried  in  fibre 
conduit  in  the  floor  to  recesses  or  cabinets  in  the  wall  at  the  right 
in  Fig.  118.  In  these  cabinets  are  the  current  and  potential 
transformers  from  which  low-tension  wires  are  taken  to  the  in- 
struments on  the  switchboard  in  the  gallery.  The  generator  leads 
then  pass  up  to  the  primaries  of  the  step-up  transformers  in  the 
transformer-cell  rooms  above.  The  5o,ooo-volt  secondary  leads 
of  these  transformers  are  connected  in  delta  in  the  transformer- 
room  and  then  pass  up  through  circular  openings  in  the  floor,  filled 
with  plate  glass,  to  the  bus-bar  cells  or  compartments,  to  which  a 
part  of  one  floor  of  the  power  station  is  devoted.  From  the  bus- 


TAYLOR'S  FALLS  PLANT 


241 


bar  cells  the  wires  lead  up  through  similar  circular  floor  openings 
to  the  5o,ooo-volt  oil  switches. 

The  oil  switches  (which  have  a  capacity  of  1,500  amperes  at 
50,000  volts)  are  considerably  larger  than  are  needed  in  this  plant. 
They  were  originally  built  for  another  plant,  but  were  sent  to 
Taylor's  Falls  because  of  the  urgency  of  delivery.  They  are  sole- 
noid-operated and  in  reality  consist  of  three  enormous  single-pole 
oil  switches  mechanically  connected.  At  the  right  in  Fig.  120  is 


FIG.   120. — 50,000  VOLT,  OIL  SWITCHES. 

seen  the  row  of  holes  left  for  the  high-tension  conductors  to  the 
second  set  of  5o,ooo-volt  oil  switches.  The  other  openings  in  the 
floor  are  recesses  left  for  oil  piping.  From  the  oil  switches  control- 
ling each  bank  of  transformers  the  conductors  pass  down  again  to 
the  5o,ooo-volt  bus-bars.  In  the  case  of  the  oil  switch  connecting 
the  5o,ooo-volt  bus-bars  to  the  transmission  line  the  wires  pass  up 
from  the  oil  switches  to  the  series  transformers  and  choke  coils 
and  thence  out  of  the  building.  The  general  arrangement  of 

16 


242       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

current  transformer,  choke  coil,  and  lightning  arrester  for  one 
phase  of  the .  50,000- volt  line  is  shown  in  Fig.  121.  Hook  dis- 
connecting switches  are  provided  on  each  side  of  all  high-tension 
apparatus  to  provide  for  its  isolation  in  case  work  is  being  done 
upon  it. 

The  operating  switchboard  is  comparatively  small  and  sim- 
ple, all  of  the  operating  switches  in  the  main  circuit  being  designed 
for  remote  control  by  low-tension  circuits.  These  low-tension  cir- 


1    3 


ONLY  ONE  PHASE  SHOWM 


FIG.  121. — CONNECTIONS  OF  TRANSFORMER,  CHOKE-COIL  AND  LIGHTNING- 
ARRESTER. 

cults  are  obtained  from  the  exciter.  There  are  two  negative  ex- 
citer bus-bars,  one  of  which  is  for  local  miscellaneous  use  in  the 
power-house  and  the  other  for  the  field  excitation.  There  is  one 
common  positive  bus.  Each  exciter  has  simply  a  double- throw, 
single-pole  switch  for  connecting  it  to  either  negative  bus-bar,  and 
an  automatic  circuit  breaker.  The  totalizing  panel  for  the  board 
forms  the  centre  of  a  semi-elliptical  arrangement  of  switchboard 
panels.  This  totalizing  panel  contains  an  indicating  wattmeter 
which,  by  means  of  a  commutating  switch,  can  have  its  connec- 
tion changed,  so  that,  when  the  load  is  light,  almost  a  full  scale 


TAYLOR'S  FALLS  PLANT  243 

reading  can  be  obtained,  applying,  of  course,  the  proper  constants 
to  the  reading  to  give  the  correct  result.  The  other  features  of  the 
board  are  those  ordinarily  found  in  such  installations. 

Gate-lijting  Mechanism. — The  main  gates  which  admit  the 
water  from  the  forebay  into  the  penstocks  are  raised  and  lowered 
by  a  motor-operated  mechanism.  A  motor  mounted  on  the  ceiling 
drives  a  shaft  that  runs  the  length  of  the  power-house.  From  this 
shaft  is  driven  a  counter-shaft  at  each  gate.  This  countershaft  has 
a  worm-gear  driving  pinions  engaging  in  racks  on  the  gate.  It  is, 
of  course,  intended  that  only  one  gate  shall  be  operated  at  a  time. 
The  mechanism  for  any  gate  can  be  brought  into  operation  by 
throwing  in  a  clutch.  The  controller  for  the  motor  is  located 
on  one  wall  of  the  building  and  is  connected  by  a  sprocket  chain 
to  a  shaft  which  has  two  hand  wheels  at  every  gate,  so  that  the 
motor  can  easily  be  stopped  and  started  from  any  point.  The 
height  of  the  water  in  the  forebay  is  continuously  indicated  and 
recorded  by  a  Frieze  water-level  recorder. 

The  regular  operating  force  of  this  station,  including  both 
night  and  day  shifts,  consists  of  one  chief  engineer,  two  operators, 
and  two  oilers. 

THE  LINE. 

The  transmission  line  is  40.6  miles  long  and  is  designed  to  carry 
the  total  present  capacity  of  the  Taylor's  Falls  plant — namely, 
10,000  K.W. — with  a  line  loss  of  6  per  cent,  and  a  voltage  drop 
of  10  per  cent.  It  is  built  in  almost  an  air  line  from  the  west  side 
of  the  St.  Croix  River  and  Taylor's  Falls  to  a  substation  at  the  city 
limits  of  Minneapolis.  At  the  Minneapolis  substation  are  step- 
down  transformers  for  reducing  from  47,500  to  13,800  volts. 
From  this  substation  the  transmission  is  at  13,800  volts  to  the  vari- 
ous stations  and  substations  of  the  Minneapolis  General  Electric 
Company. 

Pole  Line. — A  right  of  way  60  feet  wide  was  purchased  for  the 
entire  line.  The  right  of  way,  however,  is  not  fenced  in,  and  farm- 
ers are  allowed  the  use  of  the  land  just  as  before  the  purchase.  The 


244       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

general  direction  of  the  line  is  northeast  and  southwest,  so  that  it 
cuts  diagonally  across  all  fields.  As  the  highways  follow  the  sec- 
tion and  half-section  lines,  the  nearest  highway  zigzags  across  the 
line  from  one  end  to  the  other.  As  the  country  is  dotted  with  small 
lakes,  a  number  of  these  had  to  be  crossed,  and  for  such  crossings 


FIG.   122. — TRANSMISSION  LINE. 

steel  towers  were  employed.  Fig.  122  is  from  a  photograph  of  the 
typical  straight-line  construction.  This  shows  also  one  of  the 
telephone  booths.  Fig.  123  is  a  drawing  showing  the  dimensions 
on  a  standard  straight-line  pole.  The  separation  between  wires 
is  6  feet.  The  conductors  are  No.  4-0  stranded,  semi -hard-drawn 
copper.  A  four-pin  telephone  cross-arm  is  placed  7  feet  below 
the  transmission  line.  The  poles  are  set  from  100  feet  to  120  feet 


TAYLOR'S  FALLS  PLANT 


245 


apart  and  vary  in  length  according  to  the  local  conditions  and  con- 
tour of  the  country  from  40  feet  to  60  feet,  the  object  of  this  being, 


i_l_U 

FIG.   123. — STANDARD  POLE. 


FIG.   124. — GUYED  POLE. 


FIG.  125. — TRANSPOSITION  POLE. 


FIG.   126. 


of  course,  to  avoid  too  sudden  changes  in  the  level  of  the  conductors. 
The  following  pole  dimensions  were  specified: 

For  a  length  of  40  ft Tops    8  ins.,  butts  15  ins. 

For  a  length  of  50  ft ; Tops    9  ins.,  butts  16  ins. 

For  a  length  of  60  ft * Tops  10  ins.,  butts  18  ins. 


246       DEVELOPMENT   AND   DISTRIBUTION  OF  WATER   POWER 

The  cross-arm  braces  are  of  ij-inches  X  3-i6-inch  angle  iron 
3  feet,  7 f  inches  long. 

The  main  transmission  cross-arms  are  7  feet  4  inches  long  and 
5X7  inches  in  section.  There  are  in  all  12  telephone  booths 
in  40.6  miles  of  line.  There  is  a  patrolman's  cottage  at  the  half- 
way point,  the  other  patrolmen  living  at  Taylor's  Falls  and  Min- 
neapolis. For  crossing  lakes  four  sizes  of  steel  towers  are  used— 
40,  45,  50,  and  60  feet  in  height.  Conductors  are  spaced  7 
feet  apart  on  towers.  There  are  27  steel  towers  on  the  line  on 
account  of  the  large  number  of  bogs  and  lakes  to  be  crossed. 
The  telephone  wire  is  No.  10  semi-hard-drawn  copper.  Double 
cross-arms  are  used  at  all  curves  and  pronounced  changes  in  the 
profile. 

Fig.  126  is  a  drawing  giving  dimensions  and  foundation  details 


,*, 


BM 


FIG.   127. — TRANSPOSITION  OF  CONDUCTORS. 

for  use  when  crossing  a  narrow  stream.  Fig.  127  shows  the  ar- 
rangement at  the  transposition  of  the  transmission  conductors. 
A  transposition  of  one- third  turn  occurs  every  3^  miles.  A  double 
pole  is  used  for  this  purpose.  The  telephone  line  is  transposed 


TAYLOR'S  FALLS  PLANT 


247 


every  tenth  pole.     Fig.  128  shows  a  pair  of  steel  towers  at  the  cross- 
ing of  Leedholm  Lake. 

Insulators  and  Pins. — The  transmission-line  insulator  used  is 
known  as  S.  &  W.  No.  i,  made  by  Locke.     A  cross-section  of  this 


FIG.  128. — STEEL  TOWERS. 


insulator  is  shown  in  Fig.  129.  It  consists  of  four  parts  held  to- 
gether with  neat  cement.  These  insulators  are  shipped  in  crates, 
assembled,  but  without  pins.  The  crates  were  provided  with  holes 


248       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

just  the  right  size  to  take  in  the  pin.  The  cementing  in  of  pins 
was  done  before  the  insulators  were  uncrated,  the  crate  thus  serving 
the  purpose  of  a  template  to  hold  the  pins  in  position  while  the  ce- 
ment dried.  The  insulator,  as  seen  by  the  drawing,  is  12  J  inches 
high  by  14  inches  in  diameter  over  all.  The  four  parts  were  tested 
before  assembling  with  a  6o-cycle,  2oo-kilo-volt-ampere  testing  set. 


FIG.  129. — INSULATOR. 

The  top  piece  withstood  a  test  pressure  of  60,000  volts;  the  second 
shell,  40,000  volts;  the  third  shell,  50,000  volts;  and  the  fourth 
inner  shell  or  centre,  50,000  volts.  The  assembled  insulator  with- 
out cement  was  tested  at  120,000  volts. 

The  strain  insulators,  as  shown  in  the  guy  wire  in  the  illus- 
trations, consist  of  pieces  of  oak  2  J  inches  X  2^  inches  and  30  inches 


TAYLOR'S  FALLS  PLANT 


249 


long,  boiled  in  linseed  oil.  A  tie  wire  of  No.  2  solid  copper  is  used 
for  fastening  the  No.  4-0  stranded  conductor  on  the  5o,ooo-volt 
insulators. 

The   insulator  for  the  telephone  line   is  a  double  petticoat 
2,300-volt  porcelain  insulator  placed  on  a  locust  pin  with  a  white- 
pine  cross-arm.     The  cross-arms  of  the  trans- 
mission line  are  of  fir,  unpainted. 

The  pins  for  the  transmission  insulators 
are  made  from  2-inch  extra-heavy  steel  pipe, 
with  ends  swedged  down  for  cementing  into 
the  insulators.  Fig.  130  shows  the  pin  used 
on  the  cross-arms.  This  pin  is  held  by  a 
bolt  passing  at  right  angles  through  the  cross- 
arm.  The  pins  used  on  the  pole  tops  have 
their  lower  ends  flattened  so  as  to  bolt  against 
the  pole.  Two  pins  out  of  every  100  are  tested 
and  must  stand  a  lateral  strain  of  2,000 
pounds  applied  at  a  point  i  inch  above  the 
top,  without  yielding. 

Lightning  Protection. — Few  transmission 
lines  have  had  so  much  attention  given  them 
as  regards  lightning  protection.  Minnesota 
thunder-storms  are  very  severe,  and  it  was  felt 
that  with  a  line  of  so  much  importance,  upon 
which  the  electric- light  and  power  sen-ice  of 
a  great  city  might  be  dependent  there  was  every  reason  for 
obtaining  the  best  in  lightning  protection.  Of  the  lightning  pro- 
tection appliances  about  to  be  described,  many  are  of  a  partially 
experimental  nature  and  have  been  put  up  with  a  view  to  deter- 
mining points  about  which  there  is  at  present  considerable  un- 
certainty. 

At  each  end  of  the  line  and  in  the  middle,  horn-type  lightnmg 
arresters  have  been  installed  in  accordance  with  Fig.  131.  A 
rectangular  cross-arm  frame  is  built  between  four  poles,  and  the 
necessary  insulators  mounted  on  these  cross-arms.  The  horn 


FIG.  130.— INSULATOR 
PIN. 


250       DEVELOPMENT   AND   DISTRIBUTION  OF   WATER   POWER 


spark-gap    is   adjustable   from   zero  to   12   inches.     Underneath 

the  arrester  is  a  platform,  also  mounted  on  transmission  insulators. 

A  water-column  resistance  can  be  inserted  in  the  series  with  a 


FIG.   131. — HORN  LIGHTNING  ARRESTERS. 


FIG.   132. — CHOKE  COILS. 

ground  wire  from  this  arrester,  this  water-column  resistance  being 
described  later.     The  choke  coil  used  in  connection  with  lightning 


TAYLOR'S  FALLS  PLANT 


251 


Tubing, 


arresters  is  shown  in  Fig.  132.  There  is  also  a  platform  under 
these  choke  coils,  so  that  the  paper  in  the  tell-tale  spark-gaps, 
which  are  placed  in  shunt  around  choke  coils,  can  be  renewed. 
A  tell-tale  spark-gap  which  has  been  used  in  large  numbers  in 
getting  records  of  static  discharges  on  this  line  is  shown  in  Fig.  133. 
Fig.  134  shows  the  framing  used  in  connection  with  the  adjustable 
spark-gaps,  tell-tale  spark-gaps,  and  fuses  installed  for  obtaining 
records  on  discharges. 

The  water-column  resistance  before  referred  to,  which  can  be 
used  in  series  with  the  ground  wire  of  the  horn  arrester,  is  shown 
in  Fig.  135.  It  consists  of  three 
galvanized-iron  tanks  or  funnels, 
one  for  each  leg  of  the  circuit. 
These  are  mounted  on  transmis- 
sion insulators,  and  each  is  con- 
nected to  the  ground  wire  from  a 
horn  arrester.  In  the  bottom  of 
these  tanks  are  five  nozzles,  one 
or  all  of  which  can  be  turned  on 
according  to  the  amount  of  water- 
column  resistance  it  is  desired  to 
insert. 

Water  from  these  nozzles  falls 
into  a  grounded    iron    pan.     This 

iron  pan  can  be  adjusted  in  height,  as  shown  by  the  drawings,  being 
suspended  on  pulley  blocks.  The  water  supply  is  piped  to  the 
arrester  tanks  by  pipes  discharging  several  feet  above  the  tank. 
For  purposes  of  obtaining  records,  every  pin  on  every  third  pole 
of  the  transmission  line  has  been  grounded  through  a  tell-tale  spark- 
gap.  Several  experimental  schemes  of  overhead  grounds  have 
also  been  installed  on  different  portions  of  the  line  to  determine  the 
best  construction.  One  form  of  overhead  ground  is  to  place  a 
grounded  wire  at  the  centre  of  the  transmission-wire  triangle. 
Another  plan  has  been  to  place  grounded  wires  directly  above  the 
two  lower  wires  of  the  triangle.  Still  another  plan  has  been  to  place 


FIG.  133. — TELL-TALE  SPARK- 
GAP. 


252       DEVELOPMENT   AND   DISTRIBUTION  OF   WATER  POWER 

a  lightning  rod  on  each  pole  with  its  point  above  the  top  wire  of 
the  transmission  triangle.  This  lightning  rod  is  fastened  to  the 
pole,  and  is  bent  out  around  the  top  transmission  wire  to  keep  it 


a  safe  distance  away.  Another  lightning-rod  scheme  installed  is 
that  of  placing  lightning  rods  on  separate  poles  set  alongside  the 
transmission  line,  the  rods  extending  about  25  feet  above  the  level 


TAYLOR'S  FALLS  PLANT 


253 


of  the  top  transmission  wire.  Tell-tale  spark-gap  boxes  are  in- 
serted in  all  ground  wires.  The  line  is  looked  after  by  four  patrol- 
men. 

Distributing  System. — The  general  plan  is  to  decrease  the  E. 
M.F.  from  47,500  to  13,800  volts  at  the  city  limits.  From  a  step- 
down  substation  at  the  city  limits  i3,8oo-volt,  three-phase  lines 
connect  with  the  two  old  generating  stations  of  the  company,  and 


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- 

^: 

m& 

J 

^ 

,  G«I».  Iron  Funnel!  ^^ 
1  C"i  O'l  •fO  ^N. 


v  w 

^>«>" 


FIG.   135. — WATER  COLUMN  RESISTANCE. 

also  supply  energy  to  a  number  of  small  distributing  substations, 
from  which  it  is  distributed  at  2,300  volts,  three-phase,  to  large  in- 
dustries located  in  the  immediate  vicinity.  It  will  be  noted, 
therefore,  that  the  distribution  system  possesses  many  features 
which  have  not  heretofore  been  employed  to  any  extent  in  large 
city  systems. 

Substation  at  the  City  Limits. — At  the  city  limits,  at  a  main 
receiving  substation,  energy  is  received  from  the  40- mile  50,000- 
volt  three-phase  line.  The  building  is  thoroughly  fireproof,  and 


254       DEVELOPMENT   AND   DISTRIBUTION  OF  WATER  POWER 

every  precaution  has  been  taken  to  prevent  interruption  of  service, 
because  all  of  the  energy  from  Taylor's  Falls  must  pass  through 
it.  This  substation  contains  nine  goo-K.W.  transformers. 
Each  transformer  is  mounted  on  a  truck  and  can  be  run  out 
onto  a  turn-table  and  from  there  over  a  track  along  the  middle  of 
the  building  to  the  door.  The  building  is  provided  with  concrete 
floors.  Water  for  cooling  the  transformers  is  obtained  from  a 
deep  well  by  means  of  a  pump.  There  is  also  a  cooling-pond 


Ground  Wire 


FIG.   136. — LIGHTNING  ARRESTER  TERMINAL  POLE. 

adjoining  the  station  into  which  water  is  discharged  after  pass- 
ing through  the  transformers.  Water  can  either  be  circulated  from 
the  well  or  from  the  pond.  The  substation  is  provided  with  pipes 
for  transformer,  and  switch  oil,  so  that  oil  can  be  run  into  any  trans- 
former case.  There  is  also  an  oil-treating  tank  similar  to  that  in 
the  power  station,  as  described  in  the  article  on  the  power  station. 
The  second  floor  of  this  substation  is  the  switchboard  and  switch- 
room,  shown  in  Fig.  137.  The  47,5oo-volt  wires  are  kept  on  one 
side  of  the  station,  and  the  13 .800- volt  wires  on  the  other  side. 
Some  of  the  high-tension  wiring  in  the  upper  part  of  this  floor  of 


TAYLOR'S  FALLS  PLANT 


255 


the  building  is  shown  in  Fig.  138,  where  the  47, 50x3- volt  wiring  is 
seen  on  the  right.  The  general  scheme  of  the  wiring  of  this  main 
substation  is  shown  in  Fig.  139.  The  incoming  47, 500- volt  trans- 
mission line,  after  passing  the  disconnecting  switches,  choke  coils, 
and  series  transformers,  is  taken  to  a  set  of  oil  switches  and  thence 
through  another  set  of  disconnecting  switches  to  the  47,5oo-volt 
bus-bars.  The  ultimate  plan  is  to  have  two  sets  of  47,5oo-volt  bus- 
bars which  can  be  connected  with  an  oil  junction  switch.  Every 


FIG.  137. — SWITCH-BOARD  ROOM  OVER  TRANSFORMER  ROOM. 

other  bank  of  transformers  is  connected  to  one  set  of  bus-bars,  and 
the  remainder  to  the  other  set.  The  13, 800- volt  terminals  of  the 
transformers  are  connected  to  two  sets  of  bus-bars  in  a  similar 
manner.  The  city  transmission  lines  are  taken  off  from  these  lat- 
ter bus-bars  and  are  led  through  oil  switches  and  potential  and 
series  transformers  to  the  transmission  lines. 

The  i3,ooo-volt  Distribution. — There  are  three  transmission 
lines  leaving  the  main  substation,  all  of  which  lines  feed  into 
the  Main-Street  station  of  the  Minneapolis  General  Electric 


256       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 


FIG.  138. — LONGITUDINAL  SECTION  OF  MAIN  SUBSTATION  SHOWING 

WIRING. 


TAYLOR'S  FALLS  PLANT 


257 


Company.  This  station  has  heretofore  been  the  principal  gen- 
erating plant.  It  contains  both  water-power  and  steam  machin- 
ery, as  will  be  briefly  outlined  later.  This  plant  will  act  as  a 
kind  of  distributing  centre.  At  it  the  E.M.F.  will  be  decreased 


^  htfel 


60,000  Volt  Incoming  Li 


FIG.   139. — WIRING  DIAGRAM  OF  MAIN  SUBSTATION. 

to  2,300  volts  for  single-phase  distribution  for  lighting  pur- 
poses over  Jhe  entire  city  outside  of  the  downtown  district.  The 
downtown  district  is  served  with  direct  current  from  the  Fifth- 
Street  station,  which  is  connected  with  the  Main-Street  station  by 
two  i3,8oo-volt,  three-phase  lines,  from  which  energy  is  obtained 


258       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

for  operating  motor  generators,  step-down  transformers,  and  rotary 
converters.  The  company's  offices  are  in  this  substation;  the 
building  in  this  respect  is  very  similar  to  the  Edison  buildings  in 
a  number  of  the  large  cities  of  the  country.  This  station  is  well 
located  to  supply  energy  to  the  direct- current,  three-wire  network 
in  the  downtown  district.  The  district  is  limited  in  area,  extending 
only  about  half  a  mile  in  any  one  direction  from  the  substation. 


FIG.   140. — WIRING  IN  TOP  OF  SUBSTATION. 

When  the  area  increases   more  direct-current  substations  will  be 
established. 

The  details  of  the  overhead  lines  are  of  considerable  interest, 
because  of  the  use  of  an  E.M.F.  of  13,800  volts  for  general  city 
distribution.  On  the  standard  pole  top  for  the  13, 800- volt  lines 
there  are  no  lower  voltage  lines.  The  top  cross-arm  is  designed 
for  use  with  grounded  guard  wires,  as  will  be  explained  later. 
The  transmission  wires  are  placed  2  feet  apart.  On  a  pole  used 
for  both  13,800-  and  2,3Oo-volt  lines  at  a  substation,  the  2,300-volt 
lines  are  placed  on  the  lower  cross-arm.  An  elaborate  pole  fram- 
ing at  a  substation  is  shown  in  Fig.  141.  This  particular  pole 
carries  a  telephone  arm  which  is  necessary  on  some  of  the  lines. 


TAYLOR'S  FALLS  PLANT 


259 


Unusual  provisions  for  lightning  protection  on  the  13,800- 
volt  lines  had  to  be  taken  because  of  the  severity  of  the  lightning- 
storms  and  by  reason  of  the  fact  that  there  are  so  many  changes 
from  overhead  to  underground  lines.  Two  grounded  guard 
wires  are  placed  on  the  ends  of  the  top  cross-arm.  At  every  third 
pole  the  guard  wire  is  grounded  to  a  coil  in  the  bottom  of  the  pole 


Side  Elevation  Elevation  Looking  Toward  Station 

FIG.   141. — DIAGRAM  OF  POLE  HEAD  AT  SUBSTATIONS. 

hole  for  new  poles  or  to  a  pipe  driven  in  the  ground  near  the  old 
poles.     The  guard  wires  are  mounted  on  2,3Oo-volt  insulators. 

All  of  the  1 3, 800- volt  lines  are  laid  underground  except  those 
in  very  sparsely  settled  portions  of  the  city.  One  of  the  lines  lead- 
ing from  the  main  substation  to  a  secondary  substation  passes 
underground  at  two  railroad  crossings  before  it  reaches  the  under- 
ground district.  Lightning  arresters  are  placed  at  all  points  of 
change  from  overhead  to  underground.  To  do  this,  miniature 
houses  of  asbestos  lumber  were  built  on  the  pole  tops.  Fig.  136 
shows  the  exterior  appearance  of  these  houses  where  the  cable  ter- 
minals are  placed  on  the  same  poles.  Here  the  cable  is  led  up 


260       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

into  a  terminal  box  and  the  choke  coils  are  mounted  between  the 
poles.  For  the  underground,  13, 800- volt  lines,  cambric  and  paper 
insulated  cables  are  used.  Cambric  is  preferred  to  paper  because 
it  is  less  liable  to  become  injured  when  handled  roughly,  and  it  is 
less  susceptible  to  moisture.  The  cable  has  6-3  2 -inch  insulation 


FIG.  142. — SECTION  OF  DISTRIBUTING  SUBSTATIONS. 

over  each  conductor,  and  6-32-inch  over  all  conductors,  with  J-inch 
lead  sheath.  In  making  a  joint  on  this  cable,  after  the  conductors 
have  been  spliced,  each  conductor  is  wrapped  with  cambric,  and 
cambric  tape  sleeves  or  thimbles  are  used  to  hold  the  conductors 
apart  when  the  joint  is  being  finished.  The  joint,  after  being 
covered  with  lead,  is  impregnated  with  Minerallac  or  G.  E.  67  com- 
pound. The  insulators  on  the  i3,8oo-volt  overhead  lines  are  of 
the  Locke  No.  3!  type,  of  brown  porcelain,  and  are  placed  on 
birch  pins. 

Distributing    Substations. — Between  main  substation    No.   2 


TAYLOR'S  FALLS  PLANT 


261 


One  Incoming  Line 

One  Transformer  Bank 

One  Outgoing  Line 


Combined 


and  the  Main-Street  station  there  are  located  along  the  three  trans- 
mission lines  various  small  substations.  These  substations, 
which  form  an  interesting  feature  of  the  company's  distribution, 
are  intended  for  the  purpose  of 
supplying  large  power  consumers 
only,  and  each  contains  simply 
three  step-down  transformers  for 
reducing  the  E.M.F.  from  13,20x3 
to  2,300  volts,  three-phase.  There 
are  no  attendants  at  these  sub- 
stations. They  are  located  near 
large  power  users;  it  is  the  inten- 
tion to  limit  their  output  to  2,000 
K.W.  Since  more  power  than 
this  will  almost  never  be  required 
at  one  plant,  it  is  considered  bet- 
ter to  build  another  substation 
when  the  2,ooo-K.W.  limit  is 
reached  rather  than  to  increase  the 
size  of  the  existing  stations.  Both 
the  13,800,  and  the  2, 300- volt 
lines  are  delta  connected.  The 
buildings  are  of  galvanized  cor- 
rugated iron.  Since  they  are 
usually  located  in  the  railroad  and 
manufacturing  districts,  their  ap- 
pearance is  not  of  great  importance. 
Fig.  142  shows  the  interior  arrangement  of  one  of  these  distributing 
substations.  Fig.  143  shows  the  general  scheme  of  wiring  a  sub- 
station, the  three  legs  of  the  circuit  being  indicated  as  one  wire. 
The  1 3, 800- volt  lines  enter  at  one  end  of  the  building  and  pass  down 
as  shown  in  Fig.  143  through  choke  coils  and  a  new  type  of  com- 
pound switch  and  fuse  rated  at  300  amperes.  The  lightning  ar- 
resters shown  mounted  at  the  right  in  Fig.  143  are  of  the  new  type 
of  shunted-gap. 


Choke  CoU 


FIG.  143. — DIAGRAM  OF  CON- 
NECTIONS 


262       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

Main-Street  Station. — The  Main-Street  station,  which  is  located 
on  the  Mississippi  River,  in  the  heart  of  the  city,  was  the  principal 
generating  station  of  the  company's  system  before  the  circuits  from 
Taylor's  Falls  were  erected.  This  station  is  now  operated  partly 
by  water  power  taken  from  the  pondage  above  the  St.  Anthony 
Falls  dam,  partly  by  steam,  and  partly  by  electricity  brought 
in  over  the  tie  lines  from  the  main  step-down  substation  of  the 
Taylor's  Falls  system,  mentioned  in  a  previous  article.  The 
station  is  also  arranged  to  act  as  an  auxiliary  to  supplement  the 
Taylor's  Falls  system  at  times  of  low  water  or  accident. 

The  general  layout  of  the  station  consists  of  line  shafts  on 
one  of  which  is  mounted  a  i,ooo-K.W.,  13, 200- volt,  three-phase 
machine  which  can  be  used  to  drive  the  shaft  from  energy  received 
direct  from  the  Taylor's  Falls  system  or  to  be  driven  by  the  prime 
movers  in  the  station,  to  deliver  energy  over  the  i3,8oo-volt  tie 
lines  to  the  step-down  substations  of  the  Taylor's  Falls  system  or 
to  the  various  substations  scattered  through  the  wholesale  distrib- 
uting district.  The  line  shafts  are  normally  driven  by  the  water- 
wheels,  which  are  three  in  number,  with  a  total  capacity  of  2,400 
H.P.,  assisted  by  the  i,ooo-K.W.  machine  operating  as  a  motor. 
The  relay  capacity  of  the  station  is  still  further  increased  by  a 
recently  installed  i,5oo-K.W.,  2, 300- volt  steam  turbo-genera- 
tor which  is  arranged  to  deliver  energy  directly  to  the  2, 300- volt 
bus  or  through  the  tie-line  transformers  to  the  tie  lines  or  to  the 
before-mentioned  motor  on  the  line  shaft.  Energy  is  supplied  from 
this  station  for  2,3<Do-volt,  two-phase,  6o-cycle  distribution,  5oo-volt, 
direct-current  distribution  and  for  both  alternating- current  and 
direct-current  arc  circuits  from  machines  belted  to  the  line  shafts, 
from  motor-generators  and  from  constant- current  transformers. 
In  addition  to  its  use  as  a  motor  or  generator  the  i,ooo-K.W.  ma- 
chine on  the  line  shaft  is  used  as  a  synchronous  condenser  to  control 
the  power  factor  of  the  system.  The  station  is  arranged  to  allow 
the  installation  of  additional  machines  of  this  type,  and  the  general 
tendency  is  to  simplify  and  consolidate  the  apparatus. 

Fifth-Street  Station. — The  Fifth- Street  station  is  the  main  sub- 


KERN    RIVER   PLANT  263 

station  of  the  Minneapolis  system,  located  at  the  business  centre  of 
the  city,  where  it  is  in  the  proper  position  to  supply  energy  to  the 
Edison  low-tension  system  and  to  control  the  bulk  of  the  business 
lighting.  The  station  receives  energy  from  the  Main- Street  station 
and  the  Taylor's  Falls  system;  it  contains  steam  auxiliary  units 
and  storage  batteries.  The  steam  auxiliary  equipment  consists 
of  600  K.W.  rating  of  23o-volt,  direct-current,  direct-connected, 
engine-driven  generators,  1,050  K.W.  of  35-cycle  rotary  converters, 
650  K.W.  rating  (on  one-hour  discharge)  of  storage  batteries; 
two  loo-K.W.,  three-phase,  125-  and  250- volt  rotary  converters, 
and  1,125  K.W.  rating  of  i3,8oo-volt  air-blast  transformers  and 
feeder  regulators  for  the  proper  control  of  the  potentials  of  distri- 
bution from  this  station.  The  high-tension  and  a  large  part  of  the 
low-tension  apparatus  of  the  station  is  operated  from  a  remote  con- 
trol switchboard. 

KERN  RIVER  NO.  i  POWER  PLANT  OF  THE  EDISON 
ELECTRIC  COMPANY,  LOS  ANGELES. 

Abstracted  from  the  Electrical  World  o]  August  10,  17,  24,  and 

31,  I0°7- 

THE  Edison  Electric  Company  of  Los  Angeles  has  com- 
pleted and  placed  in  operation  a  power  plant  on  Kern  River, 
which,  while  not  surpassing  any  previous  records  of  high  heads 
utilized  or  length  of  transmission,  does  embody  in  its  construction 
many  distinguishing  features  some  of  which  are  pronounced  de- 
partures from  previous  practice. 

In  capacity,  the  Kern  River  No.  i  power  plant  equals  the 
rated  capacity,  20,000  K.W.,  of  the  largest  impulse- wheel  plant 
previously  in  operation,  and  in  overload  capacity  surpasses  it. 
Its  gravity  conduit,  constructed  almost  entirely  of  tunnels  ex- 
cavated through  the  mountains,  is  the  most  permanent  and  cost- 
ly hydraulic  waterway  in  the  country.  The  pressure  main,  driven 
in  the  form  of  a  tunnel,  down  the  mountain  slope,  is  probably  the 
most  unique  feature  of  the  installation  and  is  a  decided  innova- 


264       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

lion  in  power-plant  construction.  The  water-wheels  embody  new 
features  in  the  design  of  buckets,  nozzles,  and  governors.  In  the 
electrical  details  of  the  station  is  incorporated  the  most  modern 
apparatus.  The  transmission  line  is  at  present  operating  at  60,- 
ooo  volts,  which  will  later  be  raised  to  75,000  volts.  The  length  of 
transmission,  117  miles,  is  exceeded  in  only  a  few  instances.  More- 
over, the  steel  towers  and  insulators  are  of  special  design. 

The  Kern  River  is  the  southernmost  large  tributary  of  the  San 
Joaquin  River,  and  has  its  head  in  the  snow-covered  slopes  of  Mt. 
Whitney  and  neighboring  peaks  in  the  Sierra  Nevada  Mountains. 

Water  for  the  Kern  River  No.  i  plant  is  diverted  at  a  point 
about  one-half  mile  below  Democrat  Spring,  in  Kern  County, 
and  about  14  miles  up  the  river  from  the  mouth  of  the  canyon. 
A.  hydraulic  conduit,  consisting  almost  entirely  of  a  series  of  tun- 
nels, approximately  nine  miles  in  length,  conveys  the  water  through 
the  mountains  on  the  south  side  of  the  river  to  a  forebay  at  a  point 
about  900  feet  above  the  river,  and  about  two  miles  from  the  mouth 
of  the  canyon,  where  the  plant  of  the  Power  Transit  and  Light 
Company,  of  Bakersfield,  is  located. 

From  the  forebay,  the  force  main  continues  down  to  the  power- 
house in  an  inclined  tunnel.  The  power-house  is  located  on  the 
.bank  of  the  river  directly  opposite  the  intake  of  the  Bakersfield 
plant,  and  at  an  elevation  of  about  20  feet  above  the  ordinary  high- 
water  level  of  the  stream  at  that  point.  The  tail-race  of  the  sta- 
tion is  designed  so  as  to  deliver  the  water  to  the  river  immediately 
above  the  diversion  point  of  the  Bakersfield  plant. 

The  transmission  circuits  extend  along  the  Kern  Canyon  and 
cross  country  to  Los  Angeles,  117  miles  distant. 

Diverting  Dam. — The  dam  which  is  built  to  divert  the  water 
from  the  Kern  River  into  the  hydraulic  conduit  is  placed  on  bed- 
rock and  is  carried  up  to  a  point  1.25  feet  above  the  flow  line  in  the 
tunnel  conduit,  thus  insuring  a  constant  supply  as  long  as  the  res- 
ervoir created  by  the  dam  is  kept  filled.  In  excavating  for  the 
dam,  bedrock  was  found  to  exist  at  varying  depths,  the  deep- 
est portion  being  at  the  south  end  at  about  35  feet  below  the  stream 


KERN   RIVER    PLANT 


265 


bed.  A  cofferdam  was  built  to  divert  the  river  during  the  con- 
struction and  while  the  fill  overlaying  the  bedrock  was  being  ex- 
cavated. Trenches  were  then  cut  in  the  bedrock  and  holes  bored, 
in  which  steel  bars  were  driven  in  two  rows  across  the  canyon. 
The  first  layers  of  concrete  were  placed  on  the  bedrock  and  secured 
to  it  by  means  of  the  trenches  and  the  steel  bars.  Cyclopean  con- 
crete was  the  material  of  construction,  the  rock  used  being  the 
granite  found  in  the  canyon.  Many  of  the  blocks  were  of  large 


FIG.   144. — MAP  OF  KERN   RIVER   DEVELOPMENT. 

size,  some  weighing  several  tons  each.  About  1,500  cubic  yards 
of  material  were  placed  in  the  foundation  and  3,500  cubic  yards 
in  the  dam  proper. 

The  dam  is  of  the  overflow  type  as  shown  in  Fig.  145. 
Its  length  on  the  crest  is  203.56  feet  and  its  height  above 
ordinary  water-level  in  the  river  about  20  feet.  At  the  base  in 
the  thickest  part  it  is  52.81  feet  wide.  The  crest  has  a  small  angle 
with  the  horizontal,  and  is  7  feet  in  width.  The  crest  and  lower 
face  were  designed  so  as  to  give  a  true  hydraulic  curve  to  the  water 
overflowing,  and  to  attain  this  end  the  upper  15  feet  of  the  face 


266       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

was  built  with  a  batter  of  i  to  i  so  as  to  allow  an  air  space  under 
the  water.  The  theory  of  the  design  is  that  air  will  enter  this  space 
under  the  water  from  the  ends  of  the  dam,  and  that  enough  will  be 
carried  down  with  the  water  to  form  an  air  cushion.  With  from 
2  feet  to  3  feet  of  water  flowing  over  the  dam,  a  very  smooth  surface 
is  presented.  Below  the  forty-five-degree  batter  the  downstream 


FIG.  145. — CROSS-SECTION  OF  DAM. 

face  has  a  radius  of  100  feet.  The  upstream  face  has  a  batter  of  } 
inch  to  the  foot. 

Head-works. — The  head  or  diversion  works  of  the  gravity 
conduit  consist  of  an  enlarged  or  widened  section  of  the  intake  tun- 
nel with  controlling  gates  operated  by  means  of  hydraulic  cylinders. 
In  order  to  prevent  contraction  as  the  water  enters  and  to  afford 
sufficient  screen  area  to  admit  the  water,  the  tunnel  is  widened  out 
at  the  entrance  to  16  feet  6  inches.  The  screens  or  grizzlies  are 
made  of  slanting  bars  and  extend  both  in  front  and  on  the  side  of 
the  controlling  gates.  The  bars  are  J  inch  X  3  inches  and  are 
spaced  on  edge,  3  inches  between  centres,  by  means  of  2j-inch 
thimbles,  the  thimble  rods  being  4  feet  apart.  The  screen  is  20 
feet  long  on  the  slant  and  8  feet  high  and  is  supported  on  4-inch 
cast-iron  pillars. 

Behind  the  screen  and  just  above  the  gate  is  a  lo-foot  plat- 
form on  to  which  can  be  raked  any  detritus  caught  by  the  screen. 


KERN   RIVER   PLANT  267 

The  grade  at  the  entrance  of  the  diverting  tunnel  is  increased  above 
the  normal  grade  so  as  to  accelerate  the  water  from  its  state  of  rest 
above  the  intake  to  normal  velocity  in  the  tunnel  below. 

Another  important  feature  of  the  headworks  is  the  drainage 
or  sluicing  tunnel,  365  feet  in  length,  that  is  driven  through  bed- 
rock below  the  intake  at  the  south  end  of  the  dam,  penetrating  to 
the  bottom  of  the  reservoir  above  the  diverting  dam.  A  heavy 
grizzly,  built  of  7o-pound  T-rails,  protects  the  entrance  of  this 
tunnel,  and  behind  are  two  gates  operated  by  hydraulic  cylinders, 
by  means  of  which  the  tunnel  can  be  closed  or  opened  as  desired. 
The  drainage  tunnel  was  first  used  to  divert  the  water  from  above 
the  site  of  the  dam  during  its  construction  to  the  river  at  a  point 
some  distance  below  the  headworks.  Its  permanent  purpose  will 
be  to  sluice  out,  at  such  intervals  as  may  be  necessary,  any  silt 
accumulating  in  the  reservoir  above  the  dam.  The  gates  of  this 
drainage  tunnel  are  constructed  for  operating  under  a  pressure 
corresponding  to  from  35  feet  1045  feet,  depending  on  the  quantity 
of  water  flowing  over  the  dam,  the  hydraulic  cylinders  for  the  gates 
being  designed  to  move  them  under  a  head  of  20  feet  of  water  over 
the  dam,  should  a  flood  of  this  magnitude  ever  occur. 

Each  of  the  gate  openings  is  8  feet  loj  inches  high  and  3  feet 
8  inches  wide,  the  side  frames  being  of  cast  iron,  and  the  sill  a 
lo-inch  X  lof-inch  redwood  timber.  The  gates  are  built  of  5- 16- 
inch  steel  plate  and  6-mch  1 5-pound  I-beams,  the  sides  being  formed 
of  i2-inch  I-beams.  There  are  two  cast-iron  hydraulic  cylinders 
installed  in  each  gate.  The  set  for  the  east  gate  is  mounted  on 
top  of  the  concrete  operating  shaft,  the  west  set  being  placed 
directly  below,  as  there  was  not  sufficient  lateral  space  to  place  them 
both  on  the  same  level.  The  lower  cylinders  are  placed  38  feet 
8  inches  above  the  sill  of  the  gate,  and  operate  their  gate  by  lifting 
rods  26  feet  long.  The  upper  cylinders  operate  their  gate  by  means 
of  40-foot  rods.  These  lifting  rods  are  4^  inches  in  diameter,  and 
are  made  of  wrought  iron  encased  in  brass  tubing  to  prevent  rusting. 
The  gates  are  guided  at  each  side  by  four  bronze  rollers  3  inches  in 
diameter.  In  order  to  equalize  the  pull  of  the  two  cylinders  on  each 


268       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

gate  there  are  installed  two  racks  10  feet  long  and  6  inches  wide 
into  which  mesh  two  1 2-inch  pinions  mounted  on  the  top  of  the 
gate. 

The  gates  for  the  intake  tunnel  are  similarly  constructed.  The 
hydraulic  cylinders,  both  for  the  intake  gates  and  the  sluice  gates 
in  the  drainage  tunnel,  are  operated  by  means  of  oil  pressure 
supplied  by  gravity  from  a  tank  on  the  bank.  The  oil  discharged 
from  the  cylinders  is  pumped  up  to  this  tank  by  a  triplex  pump, 
electrically  driven,  a  sufficiently  powerful  hand  pump  being  in- 
stalled for  emergency  use. 

Tunnels. — The  hydraulic  conduit  of  the  Kern  River  plant  is 
noteworthy  by  reason  of  its  being  the  most  permanent  construction 
of  its  character  in  the  country.  The  Edison  Electric  Company 
after  its  14  years'  practical  experience  with  the  construction  and 
operation  of  hydro-electric  power  plants,  has  profited  by  the  knowl- 
edge gained  of  the  different  forms  of  conduit  used,  such  as  timber 
flumes,  earthen  ditches,  concrete-lined  ditches,  cement  pipe  and 
tunnels,  and  for  its  Kern  River  work  determined  that  the  most 
efficient,  and,  in  the  long  run,  economical  construction  would  be 
a  system  of  concrete-lined  tunnels.  The  expense  of  driving  the 
tunnels  was  a  large  item,  but  it  was  warranted  in  this  instance  be- 
cause of  the  large  quantity  of  water  handled  and  by  reason  of  its 
permanency  and  the  fact  that  it  will  be  subject  to  practically  no 
depreciation  losses  and  but  little  expense  for  maintenance.  An- 
other important  feature  of  the  tunnel  construction  is  that  there  will 
be  practically  no  evaporation  loss  from  the  conduit.  As  the  evap- 
oration from  the  natural  stream  of  the  Kern  River  is  estimated  to  be 
from  15  to  20  per  cent  when  the  water  is  low  during  the  summer 
months,  this  factor  will  be  an  important  one  during  periods  of 
minimum  flow.  Another  advantage  of  the  closed  conduit  is  that 
no  leaves,  sticks,  or  other  debris  can  enter  the  water  after  it  leaves 
the  head  works. 

Between  the  intake  and  the  forebay  there  are  19  tunnels  form- 
ing approximately  eight  miles  of  gravity  conduit.  The  number 
and  length  of  these  tunnels  are  given  in  the  following  table: 


KERN   RIVER  PLANT  269 


TUNNELS,  KERN  RIVER  No.   i  POWER  PLANT. 

No.  of  Tunnel.  Length  in  Feet. 

i 595-o 

2 3.J36-6 

3-  •  4,049.4 

4 496.3 

5 •  1.522.3 

6 1,805. x 

7 874.0 

8 .    -  3.815-8 

9--  •  2,049.7 

10 .     .  3,010.8 

II r' 2,587.0 

12 2  , 1  69  .  9 

'3 2,335.3 

M-.  -  4.373-7 

15....  .  3,767.5 

16 1,498.4 

17 1,898.2 

18 2,131.5 

19 794-0 


Total 42,910 .  5 

The  tunnels  are  numbered  from  the  intake  down,  Tunnel 
No.  i  being  the  intake  tunnel,  the  entrance  to  which  has  already 
been  described. 

The  tunnels  were  excavated  in  the  rough  to  be  9  feet  in  width 
and  7^  feet  from  the  bottom  to  the  spring  line  of  the  arch,  and 
9  feet  in  height  in  the  centre.  Afterward  they  were  lined  with 
concrete  6  inches  to  10  inches  thick  on  each  side  and  the  floor  paved 
with  3  inches  of  concrete,  the  net  section  thus  obtained  being 
8  feet  in  width  by  7  feet  in  height.  The  entire  surface  of  the  side 
and  floor  was  covered  with  a  cement-mortar-plaster  J  inch  thick, 
composed  of  one  part  of  cement  to  two  parts  of  sand.  At  the  cor- 
ners of  the  walls  and  floor  a  curve  with  a  3 -inch  radius  was  formed 
in  order  to  prevent  wear  at  that  point  and  also  to  smooth  up  the 
flow  of  water. 

The  section  of  tunnel  adopted  is  not  the  most  favorable  to 
give  the  highest  velocity  on  a  minimum  slope,  but  is  the  most 
advantageous  for  the  purpose,  as  by  making  a  wider  tunnel  greater 
difficulties  would  have  been  encountered  with  the  roof  of  the  tunnel 
where  it  passed  through  loose  or  shattered  formation.  The  grade 


270       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

of  the  tunnels  is  7.92  feet  per  mile,  it  being  intended  that  the  water 
should  be  carried  at  a  depth  of  6J  feet.  The  cross-sectional  area 
of  the  stream  is,  therefore,  52  square  feet,  the  wetted  perimeter  is 
21  feet,  and  the  mean  hydraulic  radius  2.5.  Assuming  the  coefficient 
of  roughness  to  be  0.012  in  Kutter's  formula,  the  conduit  has  a 
discharge  capacity  of  approximately  470  cubic  feet  per  second. 
Experiments  made  on  other  tunnels  of  the  company  indicated  that 
the  coefficient  would  be  about  the  value  stated  for  this  particular 
conduit.  Observations  made  during  the  first  few  days  after  the 
conduit  was  placed  in  service  showed  that  the  coefficient  is  even 
less  than  0.012. 

In  places  where  the  tunnels  pass  through  seamy  and  shat- 
tered formation  or  "blocky"  ground,  they  had  to  be  arched  over- 
head in  order  to  support  the  roof,  the  concrete  at  the  centre  of  the 
arch  being  from  12  inches  to  18  inches  thick.  Less  than  15  per 
cent,  of  the  length  of  the  tunnel  required  such  overhead  arching. 
Where  this  was  necessary,  it  was  placed  by  using  a  templet,  with 
lagging  overhead,  the  concrete  being  thrown  back  and  tamped  into 
place  above  the  lagging.  In  excavating  through  this  blocky 
ground,  timbering  was  necessary,  the  standard  bent  formed  of  6- 
inch  X  8- inch  sets,  spaced  4  feet  between  centres  and  holding  the 
rock  back  by  3 -inch  planks.  In  such  sections  the  timbers  were 
left  in  position  and  completely  covered  by  concrete. 

The  concrete  at  the  sides  was  tamped  into  place  behind  boards 
supported  by  vertical  forms.  Wherever  large  cavities  had  been 
blasted  out  in  driving  the  tunnels,  they  were  filled  with  back-fill  of 
riprap,  the  interstices  of  which  were  filled  with  sand  and  gravel. 
The  same  method  was  pursued  above  the  concrete  in  the  arches. 
Consequently  there  are  no  cavities  existing  between  the  bedrock 
and  the  concrete  lining  in  the  tunnels. 

In  several  places  springs  were  encountered,  and  as  the  press- 
ure that  would  be  created  by  stopping  them  up  might  be  disas- 
strous  to  the  tunnel  lining,  vents  were  installed  through  which  the 
water  can  flow  into  the  tunnel.  These  vents  consist  of  sections 
of  pipe  from  f  inch  to  3  inches  in  diameter  and  6  inches  to  8 


KERN   RIVER   PLANT  271 

inches  long,  set  in  the  floor  or  wall  and  left  open  at  both  ends. 
The  water,  being  under  higher  pressure  than  that  flowing  in  the 
tunnel,  continues  to  flow  into  the  tunnel  and  thus  relieves  it  of 
any  strain. 

Portland  cement  was  used  throughout  for  the  concrete,  the 
mixture  being  in  the  proportion  of  i,  3,  and  5.  For  the  sand  and 
aggregate,  the  granite  excavated  from  the  tunnels  was  used.  The 
rock  was  crushed  to  ij-inch  and  2-inch  size,  and  for  the  sand 
was  crushed  and  rolled  so  as  to  pass  through  a  60  screen.  As  no 
adequate  water  supplies  were  available  along  the  route  of  the 
conduit,  the  water  necessary  for  mixing  the  concrete  had  to  be 
pumped  up  from  the  river.  The  men  worked  on  two  nine-hour 
shifts,  illumination  being  furnished  by  a  construction  power  plant. 
A  total  of  1 10,000  feet  of  lumber  was  used  for  forms  on  the  concrete 
work. 

After  the  tunnels  were  completed,  two  two-wheeled  hand  carts 
with  rubber-tired  wheels  were  used  for  cam-ing  cement  and  light 
tools  for  such  finishing  and  repair  work  as  was  necessary.  They 
were  also  brought  into  service  in  stringing  the  telephone  line  that 
is  carried  throughout  the  entire  tunnel  connecting  the  power-house 
with  the  diversion  works  at  the  dam.  The  two  galvanized-iron 
wires  of  this  telephone  line  are  carried  on  inverted  T-shaped  brack- 
ets about  10  inches  from  the  roof  of  the  tunnel.  The  brackets  are 
formed  of  f-inch  pipe  with  porcelain  insulators  bolted  on  each  end 
of  the  horizontal  arm.  The  vertical  pipe  is  secured  in  the  hcles 
of  the  rock  or  cement  by  wooden  plugs. 

Timber  Flumes. — The  tunnel  work  was  planned  so  as  to  avoid, 
wherever  possible,  flumes  for  spanning  the  side  ravines  encountered 
along  the  line.  However,  in  order  to  maintain  a  good  alignment 
and  make  the  line  as  short  as  possible,  a  few  exceptions  had  to  be 
made  to  this  rule.  Some  of  these  side  ravines  leading  down  to 
the  main  canyon  and  crossing  the  line  of  the  conduit  were  on  such 
a  flat  slope  that  should  the  tunnel  be  constructed  under  the  ravines, 
the  necessary  adits  would  have  been  very  long.  This  not  only 
would  have  increased  the  cost  materially,  but  also  would  have 


272       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

added  to  the  length  of  the  line  and  the  time  required  to  do  the 
work.  At  such  points  where  there  was  no  danger  from  falling  rocks 
the  ravines  were  spanned  with  flumes.  There  are  six  of  these 
flumes,  the  number  and  length  of  which  are  given  in  the  following 
table: 

FLUMES,  KERN  RIVER  No.   i  POWER  PLANT. 

No.  of  Flume.  Length  in  Feet. 

i 1,029.6 

2 129.8 

3   (steel  and  concrete  flume) 49-9 

4 73-5 

5 167.5 

6 70.4 


Total 1,520 .  7 

All  are  constructed  of  timber  except  No.  3,  which  is  built  of 
reinforced  concrete  with  a  steel  frame. 

Fig.  146  shows  the  method  of  constructing  the  timber  flumes. 
They  are  placed  on  concrete  foundations  and  are  designed  with 
a  factor  of  safety  sufficient  to  make  their  life  from  30  to  40  years. 
The  framework  for  supporting  the  flume  box  is  of  Oregon  pine, 
being  so  designed  and  distributed  that  no  part  of  the  timber  comes 
in  contact  with  the  earth  or  is  exposed  to  the  drip  should  the  flume 
at  any  time  spring  a  leak.  In  this  way  the  life  of  the  Oregon  pine 
will  be  great. 

The  flume  box  is  built  up  of  3-inch  X  1 2-inch  planks  of  redwood 
grown  in  swamp  lands  west  of  the  Coast  Range  in  Northern  Cali- 
fornia. The  grade  of  this  lumber  is  perfectly  clear,  and  its  quality 
is  such  that  its  life  should  not  be  less  than  40  years.  The  edges 
of  all  planks  were  bevelled  so  as  to  give  J-inch  opening  on  the  in- 
side of  the  joint,  which  is  calked  with  ship  chandler's  qakum. 
The  bottom  seams  were  covered  with  hot  asphaltum,  and  i-inch  X 
6-inch  redwood  battens  were  nailed  down  over  them. 

On  the  sides  of  these  flumes  a  specially  designed  batten  is 
used.  This  is  of  i-inch  X  6-inch  redwood,  the  upper  half  being 
cut  away  on  a  curve,  permitting  asphaltum  to  be  poured  be- 
tween the  batten  and  the  side  of  the  flume.  At  the  corners  of 
the  flumes  a  quarter-round  strip  is  nailed. 


KERN   RIVER   PLANT 


2/3 


The  design  of  the  flume  above  described  has  been  thorough- 
ly tested;  and  even  if  it  should  remain  dry  for  months  in  the  hottest 
weather,  its  designers  state  that  it  may  again  be  filled  with  water 
without  having  any  perceptible  leakage. 

In  some  cases,  where  crossing  streams  that  are  apt  to  carry 
considerable  water  in  winter,  span  flumes  are  constructed. 

In  connecting  the  wooden  flume  with  the  portal  of  a  tunnel, 


FIG.   146. — WOODEN  FLUME. 

use  was  made  of  a  construction  of  a  special  nature,  which  offeis 
two  points  of  contact  between  the  wood  and  the  concrete,  and  a 
well  between  the  two,  from  which  the  water  may  be  pumped  out, 
and  any  leaks  repaired  should  these  ever  occur  between  the  wood 
and  the  concrete. 

Steel-Concrete  Flume. — The  flume  between  tunnels  No.  6  and 

No.  7  across  Laird  Canyon  is  constructed  of  structural  steel  and 

concrete.     The  whole  structure  is  carried  on  1 5-inch  steel  I-beams 

set  8  feet  10  inches  apart  and  supported  by  concrete  piers.     These 

18 


274       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER  POWER 

longitudinal  girders  carry  g-inch  steel  I-cross  beams  set  4  feet 
from  centre  to  centre,  and  on  them  is  erected  a  framework  of 
structural  steel  for  the  sides  and  bottom  of  the  flume.  The 
layers  of  expanded  metal  (ij-inch  and  3-inch  mesh)  are  used  in 
connection  with  this  framework  and,  filled  with  concrete,  form 
the  plates  enclosing  the  frame.  This  concrete  construction  is  also 
reinforced  on  the  floor  by  twisted  J-inch  rods.  The  outside  and 
inside  of  the  flume  were  then  plastered,  making  the  thickness  of 
the  reinforced -concrete  sides  and  bottom  4  inches. 

This  type  of  flume  or  conduit  has  proved  a  decided  success, 
and  while  it  cost  more  than  a  wooden  flume,  it  has  the  advantage 
of  being  as  permanent  as  the  tunnels  themselves. 

Concrete  Conduits. — In  the  lengths  of  tunnels  and  flumes  enu- 
merated forming  the  gravity  conduit  for  Kern  River  No.  i  power 
plant,  no  account  is  taken  of  the  concrete  conduits  which  connect 
some  of  the  tunnels  and  which  also  connect  the  tunnels  with  the 
flumes.  There  were  places  along  the  line  where  the  tunnel  emerged 
at  the  foot  of  a  steep  incline  in  such  a  manner  that  the  flume  if 
constructed  on  the  grade  would  be  threatened  by  landslides  or 
bowlders  rolling  down  the  side  of  the  mountain.  These  places 
were  spanned  by  means  of  concrete  conduits,  the  interior  of  which 
has  the  same  cross-section  and  slope  as  the  tunnels  themselves. 
The  walls  are  made  heavy  and  reinforced  with  steel  and  an  arch 
overhead,  the  arch  being  covered  with  a  cushion  of  earthen  material 
to  receive  the  impact  of  anything  rolling  or  sliding  down  the  hill  and 
passing  over  the  conduit.  There  are  eight  of  these  conduits,  the 
following  table  giving  the  length  of  each: 

CONCRETE  CONDUITS.  KERN  RIVER  No.   i. 

No.  of  Conduit.  Length  in  Feet. 

i 100 . oo 

2 69.4 

3 6.2 

4 42.2 

5 40-0 

6 92-5 

7 31-6 

8....                                                                           .  121. 6 


KERN   RIVER   PLANT  275 

Forebay. — A  terminal  equalizing  reservoir  of  some  size  at  the 
end  of  the  gravity  conduit  and  feeding  the  pressure  main  would  have 
been  desirable  in  connection  with  the  Kern  River  No.  i  project. 
However,  the  side  of  Mt.  Breckenridge,  where  the  lower  end  of 
Tunnel  No.  19  emerges  above  the  power-house,  is  approximately 
on  a  forty-five-degree  slope,  making  it  impossible  to  excavate  any 
large  area  for  a  terminal  reservoir  or  forebay.  It  was  necessary, 
however,  to  have  a  small  basin  for  regulating  the  flow  into  the  force 
main,  and  for  this  purpose  a  chamber  30  feet  X  42  feet  was  ex- 
cavated to  a  depth  of  about  8  feet  below  the  grade  of  the  supply 
tunnel.  Inside  of  this  and  over  the  mouth  of  the  force  main  were 
erected  controlling  gates  and  screens  through  which  the  water 
passes  into  the  force  main. 

The  walls  of  the  forebay  were  made  of  concrete  in  the  form 
of  retaining  walls  where  they  were  enclosed  in  the  excavation, 
and  on  the  lower  side  where  they  were  unsupported  they  were 
made  sufficiently  heavy  to  withstand  the  pressure  of  the  water 
on  the  inside  of  the  forebay.  As  the  formation  where  the  structure  is 
located  is  somewhat  shattered,  the  concrete  work  was  heavily  rein- 
forced and  the  floor  was  paved  with  3  feet  of  concrete.  In  the  rear 
these  walls  were  extended  up  to  a  considerable  height  to  prevent  ma- 
terial caving  from  the  mountain  above  from  dropping  into  the  forebay. 

On  one  side  is  a  spillway  9  feet  above  the  floor  of  the  forebay, 
and  consisting  of  five  82-inch  openings  over  which  the  water  flows 
into  the  waste  flume  when  it  is  desired  to  divert  part  or  all  of  the 
tunnel  flow  from  the  pressure  main.  The  height  of  this  spillway 
can  be  controlled  by  means  of  flash-boards  which  may  be  inserted 
and  removed  as  required,  according  to  the  quantity  of  water  carried 
-  through  the  tunnels.  The  extreme  height  of  the  spillway  is  3  feet. 
A  2 4- inch  gate  valve  is  set  at  each  end  of  the  spillway  for  sluicing 
into  the  waste  flume. 

The  force  main  starts  from  the  bottom  of  the  forebay,  thus 
making  it  possible  to  have  the  water  enter  it  from  opposite  directions. 
This  construction  tends  to  prevent  the  formation  of  eddies  or  a 
whirlpool  at  the  entrance. 


276       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

The  controlling  gates  have  an  opening  6  feet  2  inches  high  and 
10  feet  wide,  and  are  built  up  of  4-inch  X  1 2-inch  timbers  on  two 
vertical  6-inch  steel  I-beams.  They  are  raised  by  means  of  hand- 
operated  gearing  through  four  sets  of  gears  working  into  two 
racks  (7  inches  wide  and  3-inch  pitch)  mounted  on  the  front  of  each 
gate.  Behind  the  gates  and  inclined  upward  toward  each  other  are 
two  heavy  trash-racks.  These  are  formed  of  3J-inch  X  J-inch 
iron  straps,  spaced  3-inch  centres  by  thimbles  of  2j-inch  wrought- 
iron  pipe,  the  rows  of  thimbles  being  set  i  foot  apart.  Each  screen 
is  1 1  feet  6  inches  long  and  is  set  on  an  angle  with  its  top  supported 
by  a  4-inch  steel  I-beam.  These  two  beams  are  set  3^  feet  apart, 
the  space  between  forming  a  walk. 

Waste  Flume. — The  forebay  is  constructed  so  that  when  the 
water  is  diverted  from  the  force  main  it  passes  over  the  spillway 
automatically  into  the  waste  conduit  extending  down  the  mountain- 
side to  the  river.  This  conduit  is  of  concrete  at  the  upper  end, 
where  it  is  on  comparatively  flat  grade,  the  section  being  8  feet 
wide  and  8  feet  6  inches  high.  The  water  is  discharged  into  a 
redwood  flume  20  feet  wide,  that  carries  it  down  the  steep  slope  of 
the  hill.  As  the  slope  is  about  forty-five  degrees,  no  material  except 
soft  wood  would  stand  the  wear  due  to  the  high  velocity.  The 
spillway  flume  is  1,200  feet  long  and  it  discharges  into  the  Kern 
River  about  600  feet  above  the  power  station. 

The  flume  rests  on  4-inch  X  6-inch  stringers  bolted  to  3-inch  X 
3 -inch  X  f-inch  anchor  plates  embedded  in  concrete  footings. 
These  footings  are  spaced  8  feet  apart  and  are  securely  set,  although 
they  are  not  carried  down  to  bedrock  in  all  cases.  The  cross-beams 
of  the  flume  are  4  inch  X  6  inch  timbers,  26  feet  6  inches  long. 
The  side  posts  are  4  inches  square  and  are  carried  up  3  feet  3  inches, ' 
being  secured  at  the  bottom  by  angle  plates.  They  are  set  4  feet 
centre  to  centre,  and  are  angle-braced  by  4-inch  X  4-inch  pieces 
fastened  at  both  ends  by  J-inch  bolts.  For  lining  the  flume  2 -inch 
X  i2-inch  redwood  planks  were  used,  the  joints  in  the  floor  be- 
ing calked  and  covered  with  i-inch  X  6-inch  battens.  Quarter 
rounds  were  nailed  in  the  corners  as  in  the  other  flumes.  The 


KERN   RIVER   PLANT  277 

side  lining,  which  is  carried  up  3  feet  high,  is  battened  and 
calked  in  the  same  manner  as  already  described  for  the  smaller 
flumes. 

Pressure  Main. — The  greatest  innovation  in  the  entire  Kern 
River  No.  i  plant  is  the  pressure  main,  the  construction  of  which 
has  been  along  new  lines  and  in  decided  contradistinction  to  the 
customary  practice  of  laying  a  steel  pipe  on  the  surface  of  the  moun- 
tain slope  or  merely  burying  it  sufficiently  to  cover  it  for  protection 
against  freezing  or  expansion  and  contraction  such  as  might  be 
caused  by  a  wide  range  of  temperature  changes.  The  pressure 
main  constructed  on  Kern  River  consists  of  a  tunnel  approximately 
1,700  feet  long  driven  through  the  mountain  on  an  incline,  and 
lined  with  steel  varying  in  thickness  from  3-i6-inch  to  lA-inch. 
This  tunnel  begins  at  the  bottom  of  the  forebay,  passes  down  at  an 
angle  of  approximately  forty-five  degrees,  and,  turning  into  a  horizon- 
tal section,  emerges  at  the  lower  end  on  a  level  with  the  floor  of  the 
power  station.  There  are  three  vertical  curves  in  the  tunnel.  The 
upper  one  forms  an  angle  of  seven  degrees  260  feet  from  the  forebay 
floor.  The  second  curve,  32.5  feet  lower  down,  has  an  angle  of  five 
degrees  and  turns  the  pipe  into  a  grade  of  84.93  Pcr  ccnt-  °n  which  it 
is  carried  994.24  feet  to  vertical  curve  No.  3.  This  latter  curve  has 
an  angle  of  forty  degrees  and  from  its  lower  end  the  pipe  continues 
along  on  a  horizontal  grade  to  the  power-house,  the  total  length 
of  the  main  being  1,697  feet- 

The  pressure  main  is  finished  to  give  it  an  inside  diameter  of 
7  feet  6  inches.  At  the  top  a  taper  20  feet  long  and  10  feet  in  diam- 
eter at  the  forebay  entrance  terminates  in  the  regular  7  J-foot  diam- 
eter of  the  completed  tunnel  tube.  This  diameter  is  maintained 
throughout  the  inclined  tunnel,  and  on  the  horizontal  beyond 
vertical  curve  No.  3  for  a  distance  of  167.39  feet.  At  this  point, 
1,454.44  feet  from  the  forebay,  the  force  main  emerges  from  the 
solid  rock  and  is  carried  to  the  portal,  a  distance  of  243  feet  through 
a  detrital  deposit  lying  between  the  mountain  and  the  power-house 
site.  Where  the  tunnel  emerges  from  the  solid  rock  a  20- foot  taper 
was  installed,  reducing  the  diameter  of  the  main  from  7$  feet  to 


278       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

5}  feet,  at  which  diameter  the  pipe  is  carried  to  the  branch  piping 
at  the  power-house. 

The  inclined  part  of  the  pressure  main  and  the  portion  of  the 
horizontal  section  that  passes  through  solid  rock  were  finished  by 
installing  a  steel  lining  built  up  of  plates  3-i6-inch  thick  for  the 
incline  and  |  inch  thick  for  the  horizontal,  riveted  together  to  form 
a  cylindrical  pipe  7^  feet  internal  diameter.  The  tunnel  itself  was 
driven  in  approximately  circular  form  and  9  feet  in  diameter. 
The  steel  pipe  was  centred  in  the  tunnel,  being  installed  in  io-foot 
sections,  and  the  space  between  the  outside  of  the  steel  lining  and 
the  bedrock  was  thoroughly  filled  with  a  mixture  of  concrete,  con- 
sisting of  three  parts  sand,  three  parts  crushed  rock,  and  one  part 
Portland  cement.  The  work  of  installing  this  lining  was  begun 
at  the  lower  end  in  the  horizontal  section  where  the  pipe  is  tapered 
down  to  the  diameter  of  5.25  feet.  At  this  point  the  20- foot  taper 
already  mentioned  was  placed,  it  consisting  of  if -inch  steel  plate 
riveted  together  with  butt  straps.  The  taper  was  placed  back  in 
the  solid  rock,  and  around  it  was  constructed  a  heavy  bulkhead  of 
concrete  which  was  anchored  into  the  bedrock  by  means  of  steel 
rods  driven  into  the  sides. 

From  this  point  the  installation  of  the  light  steel  lining  with 
concrete  back-fill,  progressed  from  the  bottom  to  the  top  of  the 
tunnel,  terminating  at  the  reinforced  concrete  taper  that  connects 
with  the  floor  and  the  forebay.  The  rock  formation  through 
which  the  force-main  tunnel  was  driven  is  not  of  the  best  kind, 
being  very  much  fractured  and  broken.  It  was  necessary  to 
timber  the  greater  part  of  the  shaft  or  incline  when  it  was 
excavated,  and  these  timbers  had  to  be  removed  before  the 
steel  lining  was  installed.  The  timbers  were  removed  ahead  of 
the  steelwork,  the  bedrock  cleaned  off,  and  the  concrete  tamped 
into  place  without  difficulty.  At  a  point  about  120  feet  below  the 
top  the  men  in  charge  removed  some  timbers  without  bracing  the 
sets  above.  This  precipitated  a  cave-in  of  the  shaft,  and  several 
men  lost  their  lives,  one  man  being  imprisoned  for  two  weeks,  after 
which  time  he  was  rescued  in  good  condition.  In  retimbering  the 


KERN   RIVER   PLANT  279 

caved  portion,  octagon  steel  sets  of  y-inch,  1 5-pound  I-beams  were 
used.  These  sets  were  left  in  place  when  the  concrete  was  put  be- 
hind the  steel  lining.  The  lower  end  of  the  pressure  main,  from 
the  taper  reducing  the  diameter  to  5  J  feet  in  diameter,  was  made 
of  if -inch  steel  plate,  or  sufficiently  heavy  to  withstand  the  static 
pressure  without  any  external  support.  Xo  concrete  was  placed 
around  this  pipe,  and  the  tunnel  was  merely  left  in  its  original  con- 
dition with  the  timber  sets  to  support  the  ground  overhead. 

At  a  point  215  feet  above  the  power-house  a  manhole  was 
placed  in  the  inclined  tunnel  for  convenience  in  inspecting  and 
for  use  in  case  any  repair  work  is  necessary.  The  regular  3- 16- 
inch  steel  lining  was  replaced  at  this  point  by  a  section  of  i^-inch 
pipe  30  feet  long. 

The  steel  pipe  was  shipped  to  Camp  No.  i  at  the  power-house 
from  San  Francisco  in  5-foot  lengths,  five  sections  being  nested 
together  for  shipment.  The  outside  section  was  riveted  complete 
on  its  two  longitudinal  seams,  but  the  four  inner  sections  were 
riveted  on  one  seam  only,  so  as  to  allow  for  the  nesting.  At  the 
camp  the  pipe  was  riveted  into  lo-foot  lengths  and  hoisted  by  means 
of  an  aerial  tram  to  the  forebay  site  at  the  upper  end  of  the  pressure 
tunnel.  There  the  sections  were  secured  to  a  dolly  car,  and  lower- 
ed by  means  of  a  hoist  to  the  point  where  they  were  riveted  together. 
The  car  consisted  of  a  truck  at  each  end  of  the  pipe  section,  the 
latter  being  hung  from  two  timbers  that  passed  through  the  pipe 
and  rested  on  the  axles  of  the  trucks. 

All  the  piping  in  the  pressure  tunnel,  which  is  constructed  of 
steel  plates  of  J-inch  thickness  and  under,  is  made  up  with  standard 
lap  joints  double  riveted  on  the  longitudinal  seams  and  single 
riveted  on  round  seams.  All  pipe  on  the  work  over  J  inch  in  thick- 
ness is  made  up  of  butt-strapped  joints  throughout,  with  triple 
riveting  on  each  side  of  the  longitudinal  seams  and  double  riveting 
on  each  side  of  the  round  seams. 

After  the  steel  lining  was  completed,  an  inspection  of  it  revealed 
the  fact  that  there  were  several  places  along  the  bottom  of  the  pipe 
where  voids  had  been  formed  in  the  concrete  backing.  These 


280       DEVELOPMENT   AND    DISTRIBUTION   OF   WATER   POWER 

voids,  which  were  revealed  by  tapping,  were  caused  mainly  by  the 
difficulty  experienced  in  tamping  the  concrete  thoroughly  around 
the  sections  of  steel  lining.  The  steel  sections  were  10  feet  in 
length,  and  in  a  few  places  where  large  irregular  rock  excavation 
occurred  at  the  bottom  of  a  section  with  only  a  Q-inch  space  at  the 
top  for  handling  the  tamping  bars,  some  voids  were  naturally  formed 
because  of  the  insufficient  tamping. 

Whenever  a  void  occurred,  a  hole  was  drilled  in  the  pipe  and 
liquid  cement  was  forced  in  until  the  hole  was  filled.  The  appara- 
tus designed  on  the  spot  to  accomplish  this  work  was  an  ingenious 
one.  A  section  of  3 -inch  steel  tube  20  inches  long  was  fitted  at 
the  bottom  with  a  tap  that  would  fit  the  hole  drilled  in  the  steel 
lining.  Liquid  cement  was  poured  into  the  void  by  means  of  this 
pipe,  which  had  a  capacity  of  about  an  ordinary  pail.  When  no 
more  cement  would  run  in,  there  was  fitted  in  the  pipe  a  screw  with 
a  plunger  at  the  lower  end  and  a  crank  on  the  outer  end.  By 
means  of  this  device,  the  cement  was  forced  into  the  void  under 
pressure  until  it  would  hold  no  more.  The  pump  was  then  re- 
moved and  the  hole  in  the  lining  stopped  up  by  an  ordinary  flush 
pipe  plug.  There  were  1 16  of  these  voids  tapped  and  filled  through 
the  lining  although  only  three  of  them  were  of  large  size.  A  num- 
ber of  the  voids  required  only  a  pint  of  the  liquid  cement,  the  quan- 
tity used  varying  up  to  the  largest,  for  which  10  buckets  of  the  slush 
was  necessary.  The  slush  used  was  a  liquid  mixture  of  Portland 
cement  and  sand.  The  work  was  carried  on  from  a  dolly  car  fitted 
with  bevelled  wheels  and  lowered  down  from  the  top  by  a  steel  ca- 
ble. About  1 5  days  were  necessary  to  complete  this  special  work. 
After  all  the  voids  were  filled  the  entire  pipe  was  painted  with 
asphaltum  paint,  the  same  dolly  car  being  used  for  the  purpose. 

Although  the  design  of  the  pressure  main  has  been  criticised 
by  some,  it  is  believed  that  the  construction  will  stand  criticism 
and  will  prove  to  be  permanent,  and  for  that  reason  economical. 
The  steel  lining  has  a  low  factor  of  safety,  being  only  heavy  enough 
to  keep  its  form  and  to  resist  the  internal  pressure,  while  all  external 
pressure  is  taken  up  by  the  concrete  back-filling,  which,  backed 


KERN   RIVER   PLANT  281 

up  by  the  rock  itself,  also  resists  the  internal  pressures.  Being 
entirely  under  ground  and  some  distance  from  the  surface,  no 
trouble  will  be  experienced  by  reason  of  expansion  and  contraction 
due  to  temperature  changes.  The  anchorage  is  the  mountain  itself 
so  that  no  disastrous  effects  could  result  to  the  pressure  main  from 
any  water  ram  that  might  be  caused  by  improper  handling  of  the 
water-wheels  or  gate  valves. 

Branch  Piping. — At  the  lower  end  of  the  pressure  main  was 
constructed  the  header  pipe,  made  of  steel  plates,  van-ing  in  thick- 
ness from  i  g  inches  at  the  inner  end  to  \  inch  at  the  outer  end,  and 
consisting  of  the  following  sj>ecified  lengths  and  diameters: 

Length.  Diameter. 

33.5  ft.  .  .  43   ft.   pipe. 

23.0  ft 4 1  ft.   pipe. 

21  .o  ft 3!   ft.   pipe. 

ir  .5  ft 3      ft.   pipe. 

1 6.  7  ft 2j   ft.  pipe  at  the  end. 

These  diameters  were  graduated  to  maintain  as  nearly  uni- 
form velocity  as  possible  after  withdrawing  the  water  for  the  various 
branches  to  supply  the  water-wheel  units  in  the  power-house.  In 
reducing  the  force  main  at  the  branch  pipes  to  meet  the  diameters 
given,  the  following  taper  pipes  were  employed: 

taper 7.  5  ft.  diameter  to  5.25  ft.  diameter,  20  ft.  long. 

taper 5.25  ft.  diameter  to  4.75  ft.  diameter,  10  ft.  long. 

taper 4.75  ft.  diameter  to  4.25  ft.  diameter,  10  ft.  long. 

taper 4.25  ft.  diameter  to  3.75  ft.  diameter,  10  ft.  long. 

taper 3.75  ft.  diameter  to  3.00  ft.  diameter,  10  ft.  long. 

taper 3.00  ft.  diameter  to  2.33  ft.  diameter,  10  ft    long. 

The  branches  from  the  force  main  were  taken  off  by  means 
of  a  Y  on  the  header  pipe  and  laid  out  in  curved  form  entering  the 
power-house  at  right  angles  to  the  rear  wall.  There  is  one  branch 
28  inches  inside  diameter,  50  feet  long,  made  of  f-inch  plate,  for 
each  of  the  eight  water-wheels,  and  a  lo-inch  inside  diameter  branch 
pipe  for  each  of  the  two  exciters. 

At  the  end  of  the  last  section  of  the  force  main  is  a  28-inch  gate 
valve  which  discharges  into  the  river. 


282        DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

In  each  of  the  branch  pipes  leading  from  the  force  main  to  the 
water-wheels  are  installed  two  28-inch  gate  valves,  one  outside  of 
the  power-house  and  the  other  inside.  The  former  is  intended 
solely  for  the  purpose  of  closing  off  the  branch  pipe  in  case  of  neces- 
sary repair  to  the  gate  or  piping  inside  of  the  house.  These  outside 
gates  are  arranged  only  for  hand  drive,  while  those  inside  the  power- 
house are  equipped  for  operation  either  by  hand  or  by  electric  motor 
as  will  be  mentioned  later. 

Power-House. — The  pressure  tunnel  emerges  from  the  side  of 
Mt.  Breckenridge  at  an  elevation  above  the  sea  of  1,061.95  feet. 
Directly  in  front  of  this  point  and  slightly  upstream  there  was  a 
bowlder-covered  wash  protected  by  a  bend  of  the  river  and  bordered 
by  a  large  mass  of  bedrock  standing  at  the  edge  of  the  main  channel 
of  the  river.  This  space  was  chosen  as  the  power-house  site.  The 
intake  of  the  Power,  Transit  and  Light  Company,  of  Bakersfield,  is 
directly  across  the  stream,  and  it  is  necessary  to  discharge  the  water 
from  the  wheels  in  such  a  direction  and  at  such  an  elevation  that 
it  will  flow  by  gravity  into  their  intake. 

The  Kern  River  is  subject  at  times  to  very  considerable  floods, 
and  the  elevation  of  the  header  pipe  and  consequently  of  the  water- 
wheels  was  made  sufficiently  high  to  permit  of  running  the  units 
even  when  the  stream  is  at  its  maximum  flood. 

The  foundations  were  started  on  bedrock  and  cemented  bowl- 
ers low  enough  to  avoid  any  possibility  of  the  power-house  being 
undercut  by  floods,  and  the  walls  were  constructed  in  such  a  manner 
that  no  important  machinery  rested  on  floors  placed  on  back-fill. 
All  spaces  between  these  walls,  except  those  which  could  not  be 
utilized  on  account  of  their  falling  so  low  as  to  be  subject  to  flood, 
were  filled  in  with  compact  back-fill  from  other  portions  of  the  work. 

The  available  area  was  so  crowded  that  it  was  necessary  to 
make  a  deep  excavation  in  the  hillside  to  accommodate  the  inner 
or  eastern  end  of  the  building.  The  debris  from  this  cut  and  from 
the  tail-races  was  wasted  on  the  south  side  of  the  building  as  a 
dump  upon  which  the  header  and  branch  piping  from  the  pressure 
main  were  placed.  On  the  north  side  of  the  station  the  spoil  bank 


KERN    RIVER   PLANT 


283 


filled  in  a  triangular  area  of  the  flat  wash,  raising  its  entire  area 
above  maximum  high  water  and  producing  a  bulkhead  which  will 
protect  the  power-house  against  any  possible  flood. 

The  foundations  proper  are  of  monolithic  concrete.  The  rock 
and  part  of  the  sand  for  the  aggregate  were  secured  by  crushing 
granite  bowlders  excavated  from  the  site,  as  well  as  a  large  amount 
of  rock  which  was  lying  on  the  pressure-tunnel  dump.  Additional 
sand  was  secured  for  a  time  from  various  small  bars  in  the  river 


FIG.   147. — PLAN  OF  POWER  STATION. 

adjacent  to  the  power-house.  These  were,  however,  covered  by 
high  water  early  in  the  year,  and  after  that  time  all  necessary  make- 
up sand  was  hauled  from  the  mouth  of  the  canyon,  about  two  and 
one-half  miles  distant. 

The  upper  part  of  the  machine  foundations  carries  a  small 
amount  of  reinforcement.  The  large  block  of  masonry  back  of 
each  water-wheel  deflector  is  heavily  reinforced  and  tied  into  the 
main  foundation  blocks.  The  crane-rail  arches  for  the  interior 
wall  are  reinforced  concrete  beams,  with  the  exception  of  the  long 
span  above  the  switchboard,  which  contains  an  I-beam  girder. 


284       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

By  reason  of  the  length  of  the  building  and  the  importance  of  the 
work,  no  account  was  taken  in  its  construction  of  the  additional 
strength  resulting  from  the  continuity  of  the  beams,  the  bridging 
effect  of  the  crane  rail,  nor  its  cushioning  timbers,  nor  was  any 
allowance  made  for  the  1 2-inch  curtain  walls  which  fill  in  below 
this  beam  in  places.  The  north  wall,  however,  is  a  1 2-inch  curtain 
wall  reinforced  with  heavy  pilasters,  and  contains  only  sufficient 
reinforcement  to  render  it  reasonably  secure  against  shock  and 
vibration.  The  south  wall  of  the  building  is  of  a  cellular  construc- 
tion for  about  two-thirds  of  its  height,  in  order  to  provide  wiring 
.ducts  for  the  60,000- volt  connections.  This  wall  also  contains  only 
nominal  reinforcement.  Between  this  wall  and  the  interior  crane 
wall,  a  space  15  feet  wide,  a  series  of  transverse  partitions  break 
up  the  area  into  transformer-,  switch-,  and  switchboard-rooms. 
The  transformer-rooms  are  open  up  to  the'  crane  beam  to  permit 
of  wheeling  the  transformers  out  under  the  main  crane.  The  crane- 
rail  columns  are  not  highly  stressed  and  have  no  hooping  whatever. 
A  50-ton  electric  travelling  crane,  with  a  5o-foot  span,  serves  the 
entire  machine-room. 

The  switchboard  space  contains  a  deck  8  feet  6  inches  above  the 
floor  level,  upon  which  the  control  board  is  mounted. 

The  roof  of  the  building  is  of  galvanized  iron  laid  on  wooden 
purlins,  which  are  placed  on  steel  roof  trusses  of  52-feet  i-inch  clear 
span.  The  internal  length  of  the  machine-room  is  164  feet,  and 
its  clear  width  is  66  feet  6  inches.  The  generating  units  are  located 
along  the  north  side  of  the  station,  78  feet  from  the  centre  of  the 
pressure  header. 

Other  Hydraulic  Features. — Dead  water  leaving  the  water- 
wheels  flows  down  the  floor  of  the  wheel-race  into  the  main  tail-race. 
When  the  nozzles  are  deflected  the  water  is  diverted  past  the  buckets 
onto  a  pair  of  heavy  metal  deflector  plates. 

These  deflector  plates  are  7  feet  wide,  and  the  lower  one 
projects  out  into  the  tail-race  8  feet. 

The  speed  regulation  of  the  water-wheels  is  effected  by  a  gover- 
nor which  deflects  the  jets  of  the  two  nozzles.  The  needles  are  ad- 


KERN   RIVER  PLANT 


286       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

justed  by  hand  and  are  usually  set  to  that  maximum  size  of  jet 
which  will  be  sufficient  to  develop  the  maximum  peak  load  ex- 
pected for  that  period  of  setting  on  the  needles.  In  other  words, 
there  is  always  a  maximum  amount  of  water  leaving  the  nozzles. 
The  governor  adjusts  the  deflecting  nozzles  in  such  a  way  that  only 
as  much  water  is  directed  upon  the  buckets  as  is  needed  for  the  load 
for  the  time  being;  the  balance  discharges  below  the  buckets  into 
the  tail-race.  It  is  evident  that  at  times  when  all  load  is  thrown 
off  the  wheels,  the  governor  will  deflect  the  jets  entirely.  Each  jet 
has  a,  maximum  diameter  of  yf  inches,  and  leaves  the  nozzle  tip 
at  a  velocity  exceeding  225  feet  per  second.  It  was,  therefore, 
necessary  to  provide  means  for  receiving  the  tremendous  force  and 
for  deflecting  the  jet  into  the  tail-race. 

The  arrangement  designed  consists  of  the  pair  of  heavy  de- 
flector plates  onto  which  the  jet  is  diverted,  as  noted  above.  The 
upper  of  these  plates  consists  of  a  channel  heavily  ribbed  and  bolted 
to  the  concrete  foundation.  The  channel  at  its  upper  end  is  slight- 
ly more  inclined  than  the  deflected  jet.  Thus  the  jet  strikes  the 
bottom  of  the  channel  under  a  small  angle,  and  therefore  tends  to 
spread  and  fill  the  section  of  channel.  The  channel  gradually 
widens,  and  consequently  the  jet  is  offered  a  larger  resistance  area. 
The  lower  part  of  the  channel  is  curved,  and  at  its  end  the  jet  dis- 
charges almost  perpendicularly  downward.  The  bottom  plate  is 
S-shaped,  its  upper  end  being  flush  with  the  bottom  of  the  wheel- 
pit,  the  lower  end  practically  level.  The  jet  strikes  the  bottom 
plate  almost  in  the  turn  of  the  "  S  "  and  under  a  small  angle.  Thus 
the  jet  is  again  forced  to  spread  and  follow  the  -base  of  the  bottom 
plate.  In  due  consideration  of  the  unavoidable  wear  and  tear  of 
these  deflectors,  they  are  lined  with  removable  steel  plates  wherever 
the  surfaces  are  exposed  to  the  flow  of  the  deflected  jet,  being  held 
in  position  by  lag  screws. 

The  wheel-races  are  lined  with  steel  on  both  sides  and  fitted 
with  steel  plates  just  back  of  the  nozzle  tips  to  keep  the  splash 
water  out  of  the  shaft  alley. 

The  tail-race  is  29  feet  wide  and  extends  the  length  of  the  power- 


KERN   RIVER   PLANT  287 

house.  It  is  fitted  with  two  25-foot  steel-plate  weirs,  the  lower  weir 
at  the  end  of  the  tail-race  being  4  feet  below  the  level  of  the  upper 
weir,  which  has  its  crest  13  feet  6  inches  below  the  line  of  the  nozzles. 

The  water-wheel  branch  pipes  enter  the  power-house  at  the 
south  side  and,  after  passing  across  under  the  transformer-room 
and  before  joining  the  nozzle  bases,  connect  to  28-inch  cast-steel 
gate  valves.  These  valves  are  of  a  special  design,  and  each  is 
operated  from  the  control  switchboard  by  a  I.2-H.P.,  i2o-volt  motor. 
It  requires  7^  minutes  to  open  or  close  a  valve  by  means  of  the 
motor.  Each  gate  valve  is  equipped  with  a  4- inch  by-pass. 

In  the  machine-room  of  the  power-house  is  installed  a  Dibble 
reservoir  gauge  equipped  with  an  indicating  dial  and  a  registering 
chart  for  measurements  of  the  water  in  the  forebay. 

Construction  Plant. — A  construction  plant  generating  300  K.W. 
at  normal  rating  was  installed  for  furnishing  the  energy  used  in 
driving  tunnels,  mixing  concrete,  transporting  materials,  etc.  This 
construction  plant  was  located  at  Frenchtown,  or  Camp  5,  power 
being  developed  by  means  of  a  flume  about  800  feet  in  length  which 
supplies  water  under  4o-foot  head  to  two  McCormick  reaction  tur- 
bines each  operating  one  I5O-K.W.,  2,300- volt  generator.  This 
plant  furnished  all  the  energy  required  while  the  work  was  in  prog- 
ress, being  frequently  and  for  long  periods  operated  at  50  per  cent, 
overload,  and  was  abandoned  only  after  the  completion  of  the  main 
plant.  From  the  construction  plant,  energy  was  transmitted  at 
10,000  volts  to  all  parts  of  the  work  over  a  temporary  transmission 
line. 

Methods  oj  Construction. — It  can  be  said  that  the  methods  of 
construction  employed  were  among  the  most  modern  known  to 
engineering  practice.  For  constructing  the  tunnels,  air  compres- 
sors were  driven  by  motors  using  electric  energy  transmitted  from 
the  construction  plant,  as  already  stated,  the  air  being  piped  into 
the  various  tunnels  where  it  was  used  for  operating  pneumatic 
drills.  Ventilating  blowers  for  supplying  fresh  air  at  the  face 
of  the  tunnels  and  for  removing  the  fumes  after  a  blast  were  operat- 
ed by  electric  motors.  In  the  construction  of  the  diverting  dam,  a 


288       DEVELOPMENT   AND    DISTRIBUTION   OF   WATER    POWER 

complete  system  of  cableways  was  installed,  by  means  of  which 
material  was  transported  and  placed  in  position  in  the  dam.  In 
the  construction  of  the  power-house,  the  handling  of  materials  as 
well  as  the  crushing  of  rock  and  mixing  of  concrete  was  carried  on 
by  means  of  the  most  modern  equipment  operated  by  electric 
motors. 

Water-Wheels. — The  water-wheels  selected  for  the  Kern  River 
No.  i  plant  are  of  the  impulse  or  tangential  type.  There  are  eight 
wheels  installed,  two  for  each  of  the  four  generators.  The  two 
wheels  for  each  unit  are  overhung,  one  on  each  end  of  the  generator 
shaft,  the  unit  being  of  the  two-bearing  type.  The  water  is  pro- 
jected onto  the  buckets  of  the  wheels  through  deflecting  nozzles  of 
the  needle-valve  type  mounted  at  the  end  of  the  28-inch  branch 
pipes.  By  means  of  these  deflecting  nozzles  and  needle  valves  the 
discharge  from  the  tip  of  each  nozzle  can  be  accurately  regulated 
without  altering  the  form  of  the  jet  to  any  appreciable  extent. 

The  wheels  are  designed  to  run  at  250  r.p.m.,  and  the  two 
wheels  on  each  unit  are  guaranteed  to  deliver  a  total  of  10,750 
H.P.  to  the  generator  shaft.  Regulation  of  the  wheels  is  ob- 
tained by  means  of  self-contained  oil-actuated  hydraulic  gover- 
nors working  under  125  pounds  pressure.  The  governors  act  on 
the  nozzles  and  deflect  the  stream  off  from  or  onto  the  buckets  of 
the  wheel  as  the  load  on  the  generator  is  decreased  or  increased. 
The  governor  for  each  unit  is  placed  midway  between  the  two 
nozzles  and  is  connected  to  a  common  rock  shaft  which,  in  turn, 
actuates  the  two  nozzles  by  means  of  rocker  arms.  These  shafts 
are  below  the  main  floor  and  are  accessible  through  a  longitudinal 
shaft  alley  or  tunnel  5  feet  wide  and  having  a  clear  head  room  of 
6  feet  9  inches. 

The  nozzles  are  equipped  with  needles  for  adjusting  the  size 
of  the  stream  by  hand.  For  convenience  in  construction  and  to 
permit  of  balancing  them  for  back-thrust,  the  needles  are  straight- 
backed,  running  through  a  guide  sleeve  of  their  full  diameter  into 
a  balancing  chamber  supplied  with  water  from  the  pressure  side. 
The  needle  then  reduces  to  a  stem  and  passes  through  a  second 


KERN    RIVER   PLANT  289 

stuffing  box,  beyond  which  the  control  links  are  attached.  The 
needles  are  torpedo-shaped,  being  8  feet  long,  12  inches  in  diameter 
at  their  full  diameter,  and  8J  inches  in  diameter  at  the  stem.  The 
tip  is  about  25  inches  long  and  is  carried  down  to  a  blunt  point  on 
straight  lines.  The  needle  is  operated  by  means  of  a  hand  wheel 
on  the  main  floor,  the  wheel  stand  also  supporting  a  pressure  gauge 
connecting  with  the  nozzle,  and  the  two  pipes  connecting  the  two 
sides  of  the  nozzle  body  with  the  balancing  chamber  of  the  needle. 
Each  nozzle  throws  a  jet  7$  inches  in  diameter  at  full  opening. 

The  nozzle  casting  is  bifurcated,  the  design  being  adopted  to 
permit  of  bringing  the  needle  stem  out  without  offsetting  the 
nozzle,  as  is  done  in  other  types  of  deflecting  needle  nozzles.  The 
strain  on  the  ball-joint  bearings  is  equalized  in  this  construction. 
The  nozzle  is  a  heavy  steel  casting,  the  Y  portion  weighing  15  tons. 
A  counterbalancing  plunger  is  located  at  the  lower  end  of  each 
operating  lever  below  the  nozzle.  The  needle  stems  and  part  of 
the  tips  are  of  steel.  Some  cast-iron  tips  have,  however,  been  sup- 
plied, and  it  is  expected  that  they  will  wear  as  satisfactorily  as 
the  steel  ones. 

Each  of  the  revolving  elements  of  the  wheels  is  9  feet  8  inches  in 
diameter,  and  consists  of  a  cast-steel  rim  to  which  are  bolted  18 
bronze  buckets.  These  buckets  are  27  J  inches  wide  and  are  not 
radically  different  in  form  from  modern  buckets  used  elsewhere 
on  the  Pacific  Coast,  being  in  general  of  an  ellipsoidal  shape, 
with  a  straight  front  wall  and  a  dividing  wedge  that  dips  down 
toward  the  front  of  the  bucket. 

The  housings  of  the  wheels  are  of  cast  iron  with  graceful  lines, 
and  where  the  shaft  enters  are  fitted  with  compound  baffle  plates  or 
water  guards  to  prevent  water  escaping  from  the  housing. 

The  combined  moment  of  inertia  of  the  revolving  element  in 
the  two  water-wheels  and  generator  of  each  unit  is  W  K?  =  i  ,800,000 
pounds-feet,  by  means  of  which  regulation  at  100  per  cent,  load 
variation  is  obtained  within  less  than  8  per  cent,  when  the  units 
are  carrying  50  per  cent,  overload,  and  within  less  than  54  per  cent, 
'variation  of  speed  when  running  at  normal  load.  The  guarantee 
19 


2  QO       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

requires  that  the  water-wheel  proper  shall  develop  an  efficiency  at 
rated  load  of  82^  per  cent.,  which  guarantee  is  to  be  substantiated 
by  tests  conducted  by  the  company. 

Governors. — When  the  governor  arrangement  for  the  water- 
wheels  was  designed,  the  leading  idea  was  to  have  each  turbine  with 
its  respective  governor  form  an  independent  unit.  Although  the 
available  operating  water  pressure  of  370  pounds  from  the  force 
main  is  ample  to  operate  governors,  it  was  preferred  to  substitute 
oil  pressure.  This  precaution  is  fully  justified,  as  long  years  of 
experience  in  operating  hydraulic  governors  has  proven  that  the 
safety  is  rather  questionable,  and  the  wear  and  tear  of  the  parts 
of  regulating  valves  causes  a  constant  expense  for  repairing  and  re- 
placing parts,  which  necessitates  shutting  down  the  respective  units. 
It  was  also  deemed  preferable  not  to  feed  the  governors  with  oil 
pressure  from  a  central  system,  but  to  make  each  governor  abso- 
lutely self-contained.  The  oil  pressure  used  is  125  pounds  per 
square  inch. 

Special  attention  was  paid  to  the  safe  operation  of  the  units, 
eliminating  from  the  beginning  any  tendency  to  run  away.  For 
this  purpose,  the  arrangement  of  the  generator,  as  well  as  the 
exciter  governor,  was  made  in  such  a  manner  that  the  jets  will 
be  automatically  deflected  from  the  buckets  whenever  the  oil 
pressure  in  the  governor  should  fail. 

The  weight  of  the  two  deflecting  nozzles  for  each  unit  is  partly 
carried  by  a  hydraulic  balancing  piston  placed  midway  between 
the  nozzles,  which  receives  water  pressure  directly  from  the  force 
main.  The  governor  arm  connects  by  means  of  a  link  to  a  com- 
mon rock  shaft,  which  in  turn  actuates  the  two  nozzles  by  means 
of  rocker  arms.  The  design  of  the  connection  is  such  that  as  soon 
as  the  oil  pressure  in  the  governor  fails,  the  nozzle  will  lower  on 
account  of  the  unbalanced  weight,  and  thus  deflect  the  jet  from  the 
buckets.  The  same  result  is  accomplished  with  the  deflecting 
hood  of  the  exciter  wheels,  which  is  connected  to  a  hydraulic  water 
piston,  tending  always  to  insert  the  hood  and  thus  deflect  the  jet. 

Each  governor  is  driven  by  a  Morse  silent-running  chain  from 


KERX    RIVER   PLANT  29 1 

its  wheel  shaft.  The  connections  between  the  operating  pistons 
and  the  deflecting  nozzles  or  hoods  consist  of  levers,  pins,  links,  and 
shafts.  The  use  of  gears  or  racks  has  been  avoided,  thereby  pre- 
venting jars.which  would  result  in  lost  motion  and  wear  and  tear. 

Attention  may  be  also  called  to  the  fact  that  all  const! iuent  parts, 
as  well  as  all  accessories,  are  attached  or  combined  with  one  main 
casing,  the  advantage  being  that  each  governor  can  be  assembled 
and  thoroughly  tested  in  the  factor}',  and  shipped  completely  as- 
sembled to  its  final  destination.  The  main  casing  contains  the 
main  operating  cylinder  with  piston  and  mechanical  hand-regulating 
device.  The  oil  pump  is  attached  to  the  casing  and  immersed  in 
the  oil  reservoir.  It  is  of  the  rotary  type,  having  no  valves,  which 
are  often  the  cause  of  failure  of  oil  pressure.  The  main  pump  shaft 
also  carries  the  bevel  gear  which  drives  the  fly-balls  operating  the 
pilot  valve  over  the  regulating  lever.  The  pilot  valve  is  self-con- 
tained between  opposing  pressures,  and  any  reaction  upon  the  fly- 
balls  is  eliminated.  It  is  evident  that  this  is  a  principal  condition 
for  exact  regulation.  The  pilot  valve  distributes  the  oil  pressure 
in  the  regulating  cylinder.  The  motion  of  the  regulating  piston 
is  reversedly  transmitted  to  the  regulating  valve  by  means  of  a 
combined  compensation.  The  leverage  of  this  compensation  is 
adjustable,  so  that  the  governor  may  be  set  for  any  load-speed 
characteristic,  from  16  per  cent,  to  absolutely  constant  speed. 

The  governors  are  equipped  with  four  regulating  devices 
which  can  be  used  at  any  time:  i.  Mechanical  hand  regulation 
(without  oil  pressure).  2.  Automatic  regulation  with  fly-balls. 

3.  Hand  regulation  with  oil  pressure  (fly-balls  disconnected  by 
a  clutch  coupling  inserted  between  pump  shaft  and  fly-ball  shaft). 

4.  Hand  regulation  with  oil  pressure  and  electric  motor  operated 
from  the  switchboard.     (Synchronizing  attachment.) 

The  exciter  governors  are  of  similar  design,  except  that  they 
are  not  provided  for  electric  hand  regulation. 

There  are  two  exciter  units,  each  being  of  the  two-bearing 
type,  with  an  impulse  water-wheel  on  one  end  and  a  heavy  fly- 
wheel designed  to  give  the  unit  close  regulation  on  the  other  end 


292       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

of  the  shaft.  The  exciter  wheels  are  operated  from  stationary 
needle  nozzles,  the  needles  being  of  the  same  straight  form  used  on 
the  main  wheels.  Regulation  is  obtained  by  oil  governors  which 
operate  stream  deflectors  that  are  pulled  up  into  the  stream  from 
below  as  the  load  on  the  unit  decreases,  thus  deflecting  a  part  or 
all  of  the  stream  into  the  tail-race.  The  exciter  wheels  are  of  a  con- 
struction similar  to  the  large  wheels,  having  20  bronze  buckets 
9§  inches  wide  bolted  to  the  rim  of  the  runner. 

Generators. — The  main  generators  have  a  rated  output  of  5,000 
K.W.  each.  The  stationary  armature  is  bar- wound  for  2,300 
volts,  three-phase,  50  cycles.  Each  main  unit  is  provided  with  two 
1 6-inch  X  48-inch  babbitted  bearings,  each  fitted  with  six  oil  rings. 
In  the  pedestals  the  oil  is  cooled  by  means  of  water  coils.  Each 
bearing  also  has  in  its  lower  portion  a  number  of  small  openings 
which  are  connected  to  a  triplex  motor-driven  pump,  capable  of 
circulating  the  lubricating  oil  under  a  pressure  of  1,000  pounds  to 
the  square  inch. 

The  generator  shaft  is  flared  out  at  each  end  to  form  a  flange 
to  which  is  bolted  the  wheel  disk.  The  shaft  is  also  enlarged  at 
the  centre  to  carry  the  cast-steel  pole  rim  and  spider.  This  latter 
is  a  single  casting  weighing  twenty-six  tons.  The  pole  pieces  are 
wedged  to  the  exterior  of  this  rim. 

The  exciter  units  are  standard  225-K.W.  direct- current  ma- 
chines, generating  at  125  volts,  flat  compounded,  running  at  430 
r.p.m.,  and  have  ordinary  self-adjusting  bearings.  Sufficient 
space  has  been  left  between  the  two  exciters  to  permit  the  installa- 
tion of  a  large  induction  motor  at  some  future  time  if  it  should  be 
found  necessary.  This  motor  would  be  designed  for  good  speed 
regulation  and  arranged  so  that  it  could  be  connected  by  means  of 
a  pair  of  clutches  to  either  of  the  exciters. 

Output  o)  the  Plant. — The  normal  rated  output  of  the  Kern 
River  No.  i  power  plant  is  20,000  K.W.  The  machinery  is  tested 
to  operate  under  50  per  cent,  overload  for  peak  load  service,  thus 
making  the  maximum  capacity  of  the  installation  30,000  K.W. 

Transformers. — The  station  contains  thirteen,  5o-cycle,  1,667- 


KERN   RIVER   PLANT  293 

K.W.,  oil-filled,  shell-type,  oil-circulated,  one-phase  transformers  in 
boiler-iron  cases.  These  transformers  are  grouped  in  four  banks  of 
three  each,  with  one  spare,  to  receive  power  at  2,300  volts  delta  from 
the  generators,  and  to  supply  it  to  the  line  at  75,000  volts  Y. 
Taps  arc  also  provided  for  the  intermediate  voltages  of  56, 250  and 
37,5oo. 

These  transformers,  instead  of  having  internal  water-cooling 
coils,  are  so  built  that  when  the  oil  is  supplied  to  them  under  a  slight 
pressure  it  will  automatically  distribute  itself  throughout  their 
windings  and  return  itself  by  gravity  to  the  waste  pipe.  The  pip- 
ing and  connections  for  this  circulation,  which  are  placed  in  the 
basement  of  the  power-house,  consist  of  a  4-inch  supply  line,  a 
6- inch  return  line,  and  a  4- inch  waste.  These  principal  pipes  are 
placed  in  a  tunnel  7  feet  9  inches  wide  and  n  feet  high,  extending 
the  length  of  the  building. 

The  oil  coming  from  the  transformers  enters  a  receiving  drum 
from  which  it  is  drawn  by  two  5-inch  centrifugal  pumps,  driven 
by  I5-H.P.,  variable- speed,  shunt-wound,  direct-current  motors. 
Either  pump  can  supply  oil  to  the  entire  equipment  of  transformers 
in  an  emergency.  These  pumps  force  the  oil  through  a  set  of  boiler- 
tube  coolers  set  over  the  tail-race,  consisting  of  a  series  of  2-inch 
pipe,  10  feet  long,  made  up  in  four  sections  containing  1,008  tubes, 
and  having  a  total  area  of  4,500  square  feet.  From  these  cooling- 
coils  the  oil  returns  to  the  pressure  line,  from  which  it  is  supplied 
to  the  transformers. 

This  system  has  been  carefully  laid  out  with  strainers,  by-passes, 
and  other  auxiliaries  so  that  the  entrance  of  any  foreign  substances 
into  the  oil  will  not  cause  trouble.  As  the  system  is  under  pressure 
from  the  time  the  oil  enters  the  pump,  any  leakage  will  be  outward 
and  there  will  be  no  possibility  of  water  leaking  into  the  oil,  as  is 
the  case  where  the  water  coils  under  pressure  are  placed  in  oil- 
filled  transformers.  The  oil  is  specially  refined.  Another  ad- 
vantage of  a  system  of  this  kind  is  that  the  cost  of  installation  is 
somewhat  less  than  for  a  similar  installation  using  water- cool  ing. 

Water  for  the  cooling- sections  is  by- passed  from  one  or  both 


2 94       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

of  the  exciter  tail-races  into  a  flume  built  across  the  top  of  the 
coolers. 

Electric  Details  oj  Station. — The  generator  leads  pass  through 
ducts,  under  the  station  floor,  to  the  generator  switches,  and  from 
thence  to  the  low-tension  side  of  the  transformer  banks.  The 
station  is  not  equipped  with  a  complete  2,300- volt  bus-bar  system. 
There  are,  however,  mo  tor-operated,  oil  tie  switches  placed  between 


FIG.  149. — COOLING-COIL  FOR  CIRCULATING  TRANSFORMER  OIL. 

adjacent  machines  and  equipped  with  double- throw  switches  in 
such  a  manner  that,  in  case  of  necessity,  any  generator  can  be 
transferred  by  means  of  this  transfer  line  to  any  single  transformer 
bank,  or  run  in  multiple  with  some  other  generator  on  a  single 
transformer  bank,  or,  if  desired,  the  entire  station  can  be  tied 
together  by  means  of  this  transfer  bus  and  operated  as  a  single  unit. 
The  transformer  banks  connect  on  their  high-tension  side 
through  knife-blade  switches  to  a  single  bus-bar,  which  is  sectioned 


KERN   RIVER   PLANT 


295 


in  the  middle.  The  two  outgoing  transmission  circuits  are  tapped 
off  this  bus-bar  between  adjacent  transformer  banks  through  motor- 
operated  oil  switches.  These  switches  are  remote-control,  non- 
automatic.  By  use  of  them  and  the  section  oil  switch,  all  high- 
tension  power  switching  can  be  handled  without  the  use  of  air- 
break  switches.  At  the  same  time  the  investment  for  high-grade 
switching  is  reduced  to  a  minimum.  The  2,30o-volt  oil  switches 


FIG.  150. — SWITCHBOARD. 


are  installed  in  cells  with  concrete  barrier  walls  and  tops.  The 
disconnecting  switches  for  them  are  also  separated  by  barrier  wails 
where  possible.  The  7 5,000- volt  oil  switches  are  not  only  installed 
in  concrete  cells  in  accordance  with  standard  practice,  but  each  of 
them  is  enclosed  in  a  separate  concrete  room  containing  no  addi- 
tional apparatus  except  lightning  arresters. 

The  control  switchboard  is  mounted  on  a  gallery  overlooking 
the  machine-room.     It  is  built  of  black  slate  and  is  a  combination 


296       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER    POWER 

bench  and  panel  board,  consisting  of  nine  divisions.  The  first 
panel  on  the  left  controls  the  station  auxiliaries,  the  feeder  for 
which  is  taken  off  the  two  centre  sections  of  the  2, 300- volt  bus 
through  solenoid-operated  oil  switches  and  then  through  two  sole- 
noid-operated oil  switches  to  the  panel. 

The  second  and  third  panels  are  equipped  for  handling  the 
exciter  circuits,  and  each  is  provided  with  an  ammeter,  a  voltmeter, 
and  two  single-pole,  double-throw  knife  switches  for  connecting 
the  exciter  to  either  of  the  two  exciter  buses.  The  panel  also  has 
two  double-pole,  double-throw  switches  for  connecting  the  exciter 
bus  to  the  station  lighting  circuit  and  to  the  operating  buses  which 


FIG.   151. — DISCONNECTING  SWITCH  AND  CHOKE-COIL. 

control  the  oil- switch  motors,  the  lamps  on  the  control  board,  and 
other  auxiliaries. 

Panel  No.  4  is  blank,  while  Nos.  5,  6,  8,  and  9  are  generator 
panels.  Each  of  the  latter  is  equipped  with  three  Thomson  am- 
meters, a  field  astatic  ammeter,  a  curve-drawing  ammeter,  a  curve- 
drawing  voltmeter,  and  a  curve-drawing  wattmeter. 

The  seventh  panel  is  the  auxiliary  feeder,  bus-sectionalizing 
and  station  panel.  It  contains  a  synchronism  indicator  and  two 
voltmeters  on  the  synchronizing  bus,  an  ammeter  on  the  ground 
circuit,  and  an  ammeter  on  the  auxiliary  feeders. 

The  bench  of  the  switchboard  has  controlling  switches  with 
red  and  green  signal  lamps  for  each  of  the  four  generators,  and 
there  are  also  provided  control  switches  for  each  of  the  two  2,300- 
volt  feeder  switches,  for  the  switches  on  the  2, 300- volt  bus  sections, 
and  for  the  7 5,000- volt  outgoing  line  switches.  The  base  of  each 


KERN   RIVER   PLANT  297 

generator  bench  panel  has  one  governor  control  switch  and  a 
double-pole,  double-throw  control  switch  for  operating  the  two 
28-inch  valves  on  each  water-wheel  unit. 

On  the  six-panel  rear  switchboard  are  mounted  five  polyphase 
watt-hour  meters,  break  switches,  and  disconnecting  switches  on 
the  field  circuits.  A  curve-drawing,  frequency-registering  meter, 
driven  by  a  J-H.P.  motor,  is  also  installed. 

The  high-tension  wiring  is  run  in  4-foot  square  ducts  through- 
out, no  open  wiring  being  permitted  except  connections  from  trans- 
formers to  the  wall  through  their  disconnecting  switches,  and  from 
the  lightning  arrester  disconnecting  switches  to  the  lightning- 
arrester  banks. 

The  lightning  arresters  are  of  multiplex  type,  consisting  of 
alternate  carbon  spark-gaps  and  resistances.  The  circuits  are 
equipped  with  choke  coils,  consisting  of  20  turns  of  hard-drawn 
copper.  The  lightning  arresters  are  mounted  in  concrete-wall 
cells,  and  are  so  completely  isolated  from  each  other  by  the  inter- 
vening main-line  ducts  that  an  arc  starting  on  any  single  arrester 
could  not  by  any  possibility  be  transferred  to  a  second  bank. 

The  leads,  after  passing  the  choke  coils  and  taps  for  the  light- 
ning arresters,  pass  out  of  the  south  wall  of  the  building  through 
rectangular  openings  located  immediately  below  the  eaves.  To 
prevent  the  drip  from  the  long  run  of  roof  from  falling  on  the  wires, 
a  gutter  extends  for  a  few  feet  across  the  roof  above  each  entrance. 
From  the  eaves  of  the  building,  the  leads  converge  onto  the  first 
tower  of  the  transmission  line. 

Transmission  Line — Route. — From  the  power-house  the  trans- 
mission line  runs,  as  near  as  may  be  in  a  straight  line  to  the  mouth 
of  the  Kern  River  Canyon,  2\  miles  distant,  where  it  sweeps  off 
to  the  left  across  the  Cotton  wood  Hills,  and  then  takes  a  due  south 
course  across  the  edge  of  the  Bakersfield  plains.  The  line  then 
enters  the  mountainous  section  through  Tejon  Canyon,  follows 
across  the  end  of  Castaic  Lake,  and  crosses  the  Coast  Range  di- 
vide immediately  above  German  Station. 

This  is  the  steepest  portion  of  the  transmission  line,  as  the 


298       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 


drop  from  the  top  of  the  hill  to  the  road  below  is  over  1,000  feet  in 
3,500  feet.  From  here  south  the  transmission  line  follows  the  waters 
of  Piru  Creek  and  its  tributaries,  the  character  of  the  country 
changing  gradually  from  low,  rounded  hills  with  grassy  slopes  to 


FIG.  152. — MAP  OF  TRANSMISSION  LINE. 

deep,  narrow  gorges  walled  with  precipitous  shale  cliffs  capped  with 
sandstone  ledges. 

A  section  here  of  about  5  miles  involved  very  difficult  work. 
Heavy  angles,  both  vertical  and  horizontal,  were  necessary  in  a 
district  where  no  permanent  wagon  road  could  be  maintained 


KERN   RIVER   PLANT  299 

and  where  the  tower  footings  were  mostly  in  loose  shale.  One 
U-bend  of  the  river  was  crossed  by  means  of  a  2,250-foot  span  be- 
tween the  main  supports,  guided  by  an  entirely  unloaded  tower  at 
the  bottom  of  the  sag. 

Leaving  the  Piru  Canyon,  the  line  passes  in  an  almost  straight 
line  across  about  15  miles  of  rocky  land  covered  with  scattered  oaks 
and  chaparral.  After  reaching  the  last  crest  of  this  district,  the 
line  falls  away  rapidly  to  the  open  country  surrounding  Newhall. 
Across  this  entire  district  it  was  necessary  to  construct  a  permanent 
wagon  road  to  haul  supplies  and  permit  of  patrolling  the  line  dur- 
ing operation. 

In  the  Newhall  district,  the  line  crosses  the  San  Fernando 
Mountains  directly  west  of  the  long  tunnel  on  the  Southern  Pacific. 
Beyond  this  point  it  is  in  sight  from  the  railroad  track  most  of  the 
way  to  Los  Angeles,  and  throughout  the  greater  ]x>rtion  of  the  route 
the  line  is  erected  in  the  .open  country,  so  that  in  case  of  necessity 
it  can  be  repaired  without  excessive  delay. 

Towers. — The  transmission  line  is  carried  on  galvanized  steel 
towers,  there  being  1,140  of  these  towers.  Their  heights  range 
from  30  feet  to  60  feet.  They  are  uniformly  constructed  of  gal- 
vanized angle  iron,  bolted  with  galvanized  bolts  and  held  in  shape 
by  means  of  tension  rods.  There  are  no  compressive  braces  ex- 
cept one  pair  in  the  upper  portions  of  the  sides  and  between  the 
cross-arms.  The  nine  insulators  are  spaced  on  6-foot  centres,  five 
on  the  upper  arm  and  four  on  the  lower,  the  arms  consisting  of  9- 
inch  i3}-pound  channels. 

All  portions  of  the  tower  are  figured  to  be  safe  under  a  wind 
pressure  of  30  pounds  per  square  foot  on  the  tower  and  the  wire  of 
a  yoo-foot  span.  The  towers  will  also  withstand  absolute  failure 
of  any  single  wire,  even  though  none  of  the  resulting  strain  is  trans- 
mitted to  adjacent  wires. 

Fig.  153  illustrates  the  construction ,  of  a  standard  60- foot 
tower,  which  is  12  feet  wide  and  12  feet  across  at  the  base.  The 
uprights  are  formed  of  4-inch  angles  and  the  cross-braces  of  2J- 
inch,  3-inch,  and  3^-inch  angles,  the  diagonal  rods  being  11-16 


300       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

inch  and  f  inch  in  diameter.  Four  insulators  for  the  telephone 
lines  are  mounted  on  the  third  cross-bar,  21  feet  above  the  ground. 
Forty  of  the  towers  were  made  extra  heavy,  for  use  at  points  where 
the  line  changed  its  direction. 

The  foot-plates  of  the  towers  are  of  cast  iron,  dipped  in  asphalt, 


FIG.  153. — STANDARD  6o-pooT  STEEL  TOWER. 

and  24  inches  in  diameter.  They  are  attached  at  the  bottom  to 
4X  4- inch  foot  posts,  which  are  asphalted  on  top  of  the  galvaniz- 
ing. These  posts  are  bolted  as  extensions  to  the  corner  posts  of 
the  tower,  and  set  in  the  ground  a  depth  of  6  feet.  Tapered  holes 
were  dug  for  these  foot-plates  and  the  earth  was  tamped  back  on 
them  very  carefully.  No  concrete  footings  were  used,  except  on 


KERN   RIVER   PLANT  301 

some  special  work  in  the  city  of  Los  Angeles,  where  a  great  many 
of  the  tower  heights  exceeded  60  feet.  The  tower  parts  were  made 
as  light  as  was  consistent  with  rigid  construction.  Under  the  ex- 
treme conditions  mentioned  above,  the  factor  of  safety  in  any  steel 
member  is  specified  to  be  not  less  than  2\. 

No  cast  iron  was  permitted  in  the  construction,  except  in  the 
foot-plates.  All  connections  are  made  with  malleable-iron  castings 
with  a  factor  of  safety  of  4.  The  insulator  pins  are  of  cast  steel 
and  were  furnished  as  a  part  of  the  tower.  They  are  secured  to 
the  tower  by  four  bolts  and  are  cemented  into  the  insulators. 

The  towers  were  shipped  from  the  f acton*  knocked  down, 
with  their  small  parts  boxed,  and  were  hauled  to  their  respective 
locations  by  wagon.  They  were  assembled  lying  on  the  ground, 
and  "kicked"  into  place  by  means  of  a  gin  pole.  This  method  of 
erection  was  found  to  be  very  satisfactory  for  all  sizes  of  towers, 
and  only  such  towers  as  were  located  in  rugged  or  inaccessible  coun- 
try were  built  up  piece  by  piece. 

In  stringing  out  the  wire,  teams  were  used  with  usually  four 
animals,  although  in  limited  spaces  two  horses  on  a  tackle  were 
substituted.  Wherever  possible,  those  wires  which  could  be  lifted 
onto  the  tower  were  strung  out  alongside  and  later  on  thrown  into 
place. 

Line  Construction. — The  transmission  line  is  designed  to  con- 
sist of  three  circuits  with  the  wiring  spaced  symmetrically  on  6-foot 
centres.  This  wire  is  seven-strand,  4-0  hard-drawn  copper,  hav- 
ing an  elastic  limit  exceeding  35,000  pounds  total,  and  an  ultimate 
strength  of  62,400  pounds.  About  2,500,000  pounds  of  cable 
were  used  on  the  line. 

The  wire  was  sampled  and  tested  at  the  mill  before  being  ac- 
cepted. It  was  greased  and  shipped  on  reels  containing  usually 
two  4,ooo-foot  lengths.  Some  wire  was  also  purchased  in  shorter 
lengths  for  convenient  use  in  the  mountain  section.  No  special 
difficulty  was,  however,  experienced  in  handling  full-length  pieces 
even  in  the  most  rugged  country. 

The  type  of  clamp  used  is  shown  in  Fig.  1 54.     It  is  2  inches  long, 


302       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

and  is  constructed  of  three  pieces,  the  inner  piece  being  shaped  to 
conform  to  the  two  wires.  The  tie  wires  passing  around  the  neck 
of  the  insulator  are  of  No.  i  copper  strand.  The  four-bolt  clamps 
are  of  brass,  while  the  U-piece  placed  in  the  top  of  the  insulator 
to  prevent  chafing  is  of  No.  24  copper.  The  tie  wires  fail  in  test 
at  about  4,000  pound.  The  clamps  will  withstand  somewhat 


FIG.  154. — DOUBLE  INSULATOR  SHOWING  METHOD  OF  TYING. 

more,  and  the  construction  could  readily  have  been  made  much 
stronger  at  a  slight  additional  expense  if  it  had  been  considered 
desirable. 

The  insulators  used  are  18  inches  in  diameter,  and  the  two  lower 
petticoats  are,  respectively,  14  inches  and  n  inches  in  diameter. 
Each  assembled  insulator  weighs  50  pounds.  The  main  contract, 
for  7,500  insulators,  or  over  90  per  cent,  of  the  total  number,  called 
for  a  glaze  that  would  match  the  galvanized  steel  towers.  The 
manufacturers  were  successful  in  producing  an  insulator  with  a  light 
gray  or  slate-colored  glaze  which  harmonizes  very  well  with  the  hue 
of  the  towers.  The  resulting  construction  is  comparatively  in- 
conspicuous on  the  transmission  line,  and  the  insulators,  being  of 
this  neutral  shade,  do  not  afford  as  prominent  a  target  for  mali- 
cious marksmen  as  do  those  of  the  ordinary  brown  glaze. 

The  insulators  were  all  carefully  tested  at  the  factory  by  one 
of  the  Edison  Company's  engineers.  The  specifications  called 


KERN    RIVER   PLANT 


303 


for  a  guaranty  of  a  100,000- volt  test  from  the  groove  to  the  pin  for 
half  an  hour  under  a  precipitation  of  i  inch  in  five  minutes  at  an 
angle  of  thirty  degrees  from  the  vertical.  The  assembled  insulator 
was  required  to  withstand  under  a  wet  test  a  potential  of  150,000 


FIG.   155. — SECTION  OP  INSULATOR. 

volts  for  30  seconds,  and  the  separate  parts  are  guaranteed  to  with- 
stand a  voltage  of  25  per  cent,  in  excess  of  the  normal  proportion 
of  over-voltage  test. 

The  insulators  are  guaranteed  to  withstand  a  side  strain  of 
4,000  pounds  and  actually  fail  at  approximately  9,000  pounds.  The 
wire  has  an  ultimate  strength  of  61,300,  but  its  elastic  limit,  as 
noted  above,  will  not  much  exceed  35,000.  The  normal  failing 
point  of  the  ties,  4,000  pounds,  is,  therefore,  sufficiently  high  for 
safe  construction,  while  they  are  not  so  strong  as  to  stand  more 
than  the  wire  or  the  insulators. 

The  transmission  line,  as  stated  elsewhere,  is  carried  on  spans 
as  long  as  the  character  of  the  country  would  permit  with  towers 
not  exceeding  60  feet  in  height.  This  maximum  height  was  de- 
termined upon  as  being  that  which  would  give  the  lowest  total 


304       DEVELOPMENT   AND    DISTRIBUTION   OF   WATER   POWER 

cost  of  construction.  The  sags  for  the  different  spans  being 
determined  and  the  telephone  clearances  from  transmission 
wires  being  assumed  at  a  minimum  of  7  feet,  it  was  necessary 
to  determine  the  tower  spacings  with  minimum  safe  ground 
clearances  in  the  different  portions  of  the  line.  In  order  to  do  this 
accurately,  survey  parties  were  sent  over  the  entire  line,  taking 
tower  locations,  and  determining  all  elevations  so  that  they  were 
able  to  plot  a  profile  of  the  transmission  system  showing  the  ele- 
vation of  each  tower,  the  height  of  the  intermediate  elevations  and 
the  important  topography  of  the  country.  The  parties  designated 
the  height  of  the  tower  while  in  the  field,  making  their  profile  as 
they  went  along,  and  checking  the  resulting  line  before  leaving  that 
section  of  the  country. 

A  telephone  circuit  is  carried  the  entire  length  of  the  trans- 
mission line,  being  supported  on  the  towers  about  20  feet  above 
the  ground.  Between  towers  the  wires  are  held  up  by  wooden  poles, 
two  poles  being  necessary  between  towers  for  an  average  yoo-foot 
span. 

Switching  Stations. — The  transmission  lines  are  carried  through 
from  one  end  to  the  other,  with  transpositions  only  at  switching 
stations.  There  are  at  present  only  three  such  buildings,  at  Tejon, 
Castaic,  and  San  Fernando,  the  latter  two  of  which  contain  trans- 
former substations. 

The  switching  station  proper  is  equipped  with  two  sets  of  oil- 
break  switches  for  each  line  and  two  sets  of  knife-blade  disconnect- 
ing switches  for  each  line.  The  oil  switches  are  connected,  one 
set  after  another,  into  a  complete  circle.  After  passing  through 
the  disconnecting  switches,  the  incoming  lines  are  tapped  between 
alternate  oil  switches.  From  the  vacant  jumpers  left  after  these 
lines  have  been  tapped  in,  their  corresponding  outgoing  circuits  are 
taken,  and,  after  passing  through  the  disconnecting  switches,  leave 
the  building  on  the  opposite  side. 

The  switching-station  buildings  are  constructed  of  concrete  in 
the  most  substantial  manner.  The  circuits  are  isolated  from 
each  other  by  means  of  concrete  barriers  and  floors.  Individual 


KERN   RIVER   PLANT  305 

leads  of  the  same  circuit  are,  however,  run  in  the  same  compart- 
ment. In  spite  of  the  large  number  of  crossings  called  for  by  the 
wiring  diagram,  the  dimensions  of  the  building  are  not  excessive. 
The  Castaic  substation  is  66  feet  long  and  41  feet  6  inches  wide, 
with  a  cross-partition  wall  forming  the  switch-room.  40  feet  wide, 
and  the  transformer-room  26  feet  wide.  Provision  has  been  made 
to  connect  horn  lightning  arresters  to  the  circuits  at  these  sub- 
stations if  it  is  found  necessary  after  the  line  has  been  operated  for 
some  time. 

The  two  transformer  substations  have  in  their  switching- 
houses  an  arrangement  identical  with  that  in  the  other  stations, 
except  that  openings  were  made  in  the  west  wall,  through  which 
leads  were  taken  into  the  adjacent  transformer- house.  The  two 
were  built  together  under  the  same  roof  and  with  continuous  side 
walls  so  that  there  is  on  the  exterior  little  to  indicate  the  difference 
between  the  two  ends  of  the  station.  In  the  transformer-house  pro- 
vision has  been  made  for  two  banks  of  2,ioo-K.\V.  transformers 
from  the  transmission  line  at  60,000  volts  and  delivering  to  the  dis- 
tribution at  30,000.  The  high-tension  leads  arc  tapped  from  two 
of  the  outgoing  60,000- volt  circuits  in  the  switching- house,  and 
after  passing  through  oil  switches  join  in  a  common  bus  from  which 
the  transformers  can  be  separated  by  means  of  knife-blade  switches. 

This  switch-gear,  with  the  exception  of  the  transformer  switches, 
is  on  a  concrete  deck  forming  a  complete  second  story  in  the  switch- 
ing-house, 1 8  feet  above  the  floor.  On  the  under  side  of  this  floor 
there  are  also  mounted  the  insulators  for  the  3o,ooo-volt  circuits. 
The  30,000- volt  oil  switches  are,  however,  placed  on  top  of  the  floor. 
The  lightning  arresters  for  the  6o,ooo-volt  circuits  are  on  the  wall 
between  the  transformer,  and  the  switch-house,  and  are  separated 
from  each  other  by  6-foot  barriers,  while  the  3o,ooo-volt  arresters 
are  against  the  end  of  the  substation  immediately  below  the  oil 
switches  and  the  outgoing  3o,ooo-volt  circuits. 

At  Castaic  there  will  be  installed  at  present  one  bank  of  trans- 
formers, 2-100  K.W.,  oil-filled  and  water-cooled.  These  trans- 
formers will  supply  power  to  a  3o,ooo-volt,  4o-mile  transmission 


(Li 


KERN   RIVER   PLANT  307 

system  now  being  built  by  the  Ventura  County  Power  Company, 
west  from  Castaic  to  Saticoy,  where  a  branch  is  taken  off  at  Ox- 
nard,  while  the  main  line  continues  to  Ventura.  This  branch  will 
eventually  be  continued  to  Santa  Barbara,  30  miles  farther,  where 
the  Edison  Electric  Company  has  extensive  power  and  railway 
holdings. 

At  San  Fernando  is  a  i,2oo-K.\Y.  bank,  which  will  supply 
power  at  2,300  volts  to  lamps  and  motors. 

Los  Angeles  Receiving  Station. — The  Kem  River  Xo.  i  trans- 
mission line  terminates  in  Ix>s  Angeles,  117  miles  from  the  power 


FIG.  157. — LINES  ENTERING  Los  ANGELES  RECEIVING  STATION. 

plant,  at  the  steam  and  transformer  station  known  as  Los  Angeles 
No.  3.  This  station  is  constructed  to  receive,  transform,  and  dis- 
tribute to  the  local  substations,  power  transmitted  from  the  com- 
pany's water-power  plants  on  Santa  Ana  River,  Mill  Creek,  Lytle 
Creek,  and  Kern  River,  and  also  contains  a  large  steam  auxiliary 
plant  to  supplement  the  water-generated  power.  It  receives  power 
at  60,000  and  30,000  volts,  and  generates  and  distributes  at  16,000 
and  2,300  volts. 

Both  of  the  Kern  River  circuits  enter  the  station  through  the 
east  gable,  as  shown  in  Fig.  156.  After  passing  through  choke 
coils  the  lines  enter  oil  switches  which  connect  them  to  their  re- 


308       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

spective  bus-bars.  There  is  also  an  oil  tie  switch  between  the  two 
buses.  Each  transformer  has  an  oil  switch  which  can  be  connected 
by  means  of  a  double-throw  knife-blade  switch  to  the  bus-bars  be- 
longing to  the  west  or  to  the  middle  circuit.  When  the  east  circuit 
comes  in,  it  will  have  a  pair  of  oil  switches  so  that  it  can  be  run  on 
either  of  the  bus-bars. 

There  are  four  step-down  4,5oo-K.W.  transformer  banks,  with 
their  secondaries  wound  for  either  16,000  or  32,000  volts.  Under 
ordinary  conditions,  all  energy  received  from  Kern  River  will  be 
handled  through  the  double  i5,ooo-volt  bus.  The  transformers 
are  cooled  by  forced-oil  circulation.  The  oil,  after  leaving  the 
transformer,  is  handled  in  the  same  manner  as  at  Kern  River. 
It  enters  a  receiver,  is  forced  by  variable-speed  centrifugal  pumps 
into  boiler-tube  cooling  coils  outside  the  building,  and  passes  back 
into  the  pressure  line  which  fills  the  transformers.  There  being 
no  extensive  supply  of  cold  water  available,  the  cooling  water  is 
circulated  continuously  from  the  oil  cooler  basin  into  elevated 
troughs,  from  which  it  drops  over  a  series  of  screens,  where  it  is 
cooled  immediately  before  falling  on  the  section  containing  the 
hot  oil. 

This  building  also  contains  provision  for  switching  the  old 
30,000- volt,  8o-mile  transmission  line,  fed  by  the  Santa  Ana  and 
Mill  Creek  plants,  with  its  various  branches  and  all  the  15,000 
volt  distribution  around  Los  Angeles.  The  arrangement  of  the 
various  circuit  bus-bars,  oil  switches,  and  the  transformers  is  shown 
in  the  accompanying  diagram.  All  switches  and  circuits  are  con- 
trolled from  a  12 -panel  switchboard  on  the  gallery  of  the  turbine- 
room,  which  is  equipped  with  the  necessary  control  switches  and 
instruments  for  the  60,000-,  30,000-,  15,000-,  and  2,3oo-volt  buses. 

All  bus-bar  wiring  connections  to  the  transformers  and  the 
outgoing  circuits  are  carried  in  ducts.  In  the  new  portion  of  the 
station  these  are  filled  with  15,000- volt  leaded  paper  cables  of  211,- 
ooo-cm.  cross-sectiori,  with  the  exception  of  those  for  the  turbo- 
generator, which  has  4oo,ooo-cm.  cables. 

There  were  installed  in  the  steam  end  of  this  plant  during 


KERN   RIVER  PLANT 


3°9 


310       DEVELOPMENT   AND   DISTRIBUTION   OF   WATER   POWER 

1903  two  2,ooo-K.W.  2,3oo-volt  turbo-alternators,  with  4,000  H.P. 
of  water-tube  boilers,  in  5OO-H.P.  units.  When  it  became  nec- 
essary to  order  an  extension  for  the  plant,  in  1905,  larger- size  ap- 
paratus was  determined  upon  throughout.  An  additional  5,250 
H.P.  in  750-H.P.  units  was  installed  in  the  boiler-room. 

The  turbine  installation  in  the  new  plant  consists  of  a  single 
6,ooo-K.W.  turbo-alternator,  with  condensing  equipment.  This 
unit  is  four-stage,  single-flow,  and  is  operated  at  from  27^-inchto 
28-inch  vacuum.  Thus  far  loads  up  to  10,000  K.W.  have  been 
carried  on  the  machine  without  any  indication  of  its  maximum 
load  being  approached. 

The  generator  is  wound  for  16,500  volts,  star  connected,  and 
is  run  with  grounded  neutral  on  the  5o-cycle  distribution  of  the 
company.  The  generator  operates  perfectly  and  runs  in  mul- 
tiple with  the  main  system  without  causing  any  disturbance  what- 
ever. Between  the  neutral  of  the  machine  and  the  station  ground 
wire,  a  potential  difference  of  several  hundred  volts  exists  under 
operating  conditions,  with  the  machine  in  connection  with  star-to- 
delta-connected  transformer  banks.  This  voltage  and  the  re- 
sultant flow  where  the  neutral  switches  close,  vary  with  the  number 
of  transformers  and  the  load  on  them,  but  does  not  appear  to  vary 
from  other  causes.  An  observation  of  the  wave  shape  across  the 
neutral  connection  showed  a  somewhat  peaked  potential  wave  at 
three  times  the  frequency  of  the  main  circuit.  For  the  present,  the 
exchange  current  is  limited  by  the  insertion  of  the  choke  coil  in  the 
neutral  connection.  At  a  later  date  a  resistance  will  be  substi- 
tuted for  the  coil.  This  phenomenon  in  one  shape  or  another 
is  observable  on  all  Y- connected  four- wire  generator  installations. 

A  transformer  bank  stepping  from  15,000  to  2,200  volts  is 
connected  to  the  machine  leads  so  that  the  auxiliaries  can  be 
transferred  to  the  generator  leads  after  the  unit  is  in  full  operation. 


INDEX 


ALTERNATING-CURRENT  DYNAMOS,  76 
Alternating  currents,  71-73 

3-phase,  73 

Alternations  of  dynamos,  80 
Aluminum  conductors,  114,  182 
Ammeters,  148 

connections  of,  148 
Ampere,  71 
Animas  Power  and  Water  Co.,  hydraulic 

development  of,  176 
Appendix:    Computation    of    pressures 

set  up  in  long  pipes,  152 
Arches  under  power-houses,  39,  40 
Armature  windings,  76,  79 

insulation  of,  158 

Arrangement  of  wires,  115, 175, 190,  258 
Arresters,     lightning.     See     Lightning 

arresters. 

Automatic  speed  governors,  68 
Auxiliary  steam  plants,  2,  13,  215,  262, 

263 

BARBED  WIRES  for  lightning  protection, 

i35»  !4° 

Basins,  settling,  49,  50 
Basis  of  computing  power,  2 
Bearings,  thrust,  63,  222 

water-cooled,  181,  291 
Belt-driven  units,  75 
Bevel  gearing,  63 
Booms,  166,  222,  231 
Bulkhead,  44 

Bus-bars,  91,  150,  192,  308 
By-pass  valves,  180,  198 

CABLES,    underground,  191,  192,    259, 

260 

Canals  and  flumes,  32 
Centre  of  gravity,  16 
Chain  hoist,  49 
Choke  coils,  136,  241,  250,  297,  308 

connections  for,  136 
Chutes,  ice.     See  Ice  chutes. 

log.     See  Log  chutes. 
Circuit  breakers,  149,  150 

automatic,  146 


Circuits.     See  Conductors;  Direct  cur- 
rent; Transmission  lines;  Wires 
single-phase.     See  Single-phase    sys- 
tems. 

three-phase.     See   Three-phase    sys- 
tems. 

Circular  mils,  100 
Computation  of  jxnvcr,  2,  10 
Computation  of  pressures  set  up  in  long 

pipes,  152 

Concrete  conduits,  274 
Concrete     dams.       See     Dams,     con- 
crete. 
Conductors: 

aluminum,  114,  182 

arrangement  of,   115,   175,   190,  244, 

258 
distance  between,  119,  175,  182,  244, 

258,  299,  301 

exit  from  power-houses,  132,  297 
heat  liberated  on  passage  of  current, 

.    87 

ice-coating  on,  120 

length  of  spans  of,  120,  160 

resistance  of,  100 

sag  in,  118 

standard,  100 

steel  for  lotig  spans,  160 

supports  for  long  spans,  16 

swinging  of  suspended,  131 

telephone,  162 

transposition  of,  116,  162,  190,  246 

underground,  191,  192,  259,  260 
Conduits,  concrete,  274 
Converters,    rotary.     See    Rotary    con- 
verters. 
Copper  wire,  101.     See  also  Wires. 

current-carrying   capacity,    of    103 

hard-drawn,  101,  190,  301 

investment  in,  in 

variation   in  amount    required    with 

voltage,   103 

Core  walls  for  i-arth  dams,  27 
Cost  of  equipment,'  163 
Couplings: 

clutch,  1 86 


3I2 


INDEX 


Couplings,  flexible,  187,  188 

insulated,  187-188. 
Cranes,   travelling,   48,    169,    207,    214, 

233>   284 

Crib  dams.     See  Dams,  crib. 
Cross  arms,  122,  246 

bracing  for,  123,  246 

treatment  of,  123 
Cross-section  of  streams,  measurement 

of,  6 
Current : 

alternating.     See     Alternating     cur- 
rents. 

continuous.     See  Direct  current. 

direct.     See  Direct  current. 

heating  due  to,  87 
Curve  of  rear  face  of  dams,   29,   196, 

266 

Cyclopean  masonry,  30,  265 
Cylinder  gates,  53 

DAMS,  5,  16 

of   Animas  Power  and  Water    Co., 
177 

centre  of  gravity  of  cross-section  of, 
16 

concrete,  30,  172,  183,  196,  209,  265 

crib,  2.8,  170,  177 

curve  of  rear  face  of,  29,  196,  266 

design    of,    to    withstand    maximum 
floods,  5,  195 

drain  gates  in,  31 

earth,  26,  170,  177 

foundations  of,  25,  196,  290 

frame,  28 

gravity,  24,  30,  209 

of  Great  Falls  plant,  195 

important  factors  in  designing,  25 

of  Kern  River  plant,  264 

of  McCall  Ferry  plant,  216,  224 

masonry,  29,  218,  231 

middle  third  of,  23 

overturning  forces  on,  20,  23 

pressures  against,  18 

spillway  of,  25-196 

Taylor's  Falls  plant,  230 

timber,  27 

Trenton  Falls  plant,  209 

West  Buxton  (Me.),  165,  170 
Deflecting  nozzles,  67,  68,  180 
Design  of  hydro-electric  power  stations, 

38 

Detectors,  ground,  149 
Development,    of  Animas  Power   and 
Water  Co.  (Colorado),  176 

atDrammen  (Norway),  183 

at  McCall  Ferry  (Pa.),  215 


Development,  of  Southern  Power  Co., 
at  Great  Falls,  193 

at  Taylor's  Falls  (Minn.),  230 

at  Tofwehult   (Sweden),    154 

at  Trenton  Falls  (N.  Y.),  208 

at  West  Buxton  (Maine),  164 
Direct  current,  81,  162,  174 

from  transmission  lines,  162,  174,  258 
Division  of  power  among  units,  76 
Draft  chests,  58 

Draft  tubes,  39,  44,  52,  56,  203,  205, 
220,  233 

depth  submerged,  59 

proportions  of,  59 

velocity  of  flow  in,  59 
Drain  gates,  31 

Drammen  (Norway)  development,  183 
Drop,  inductive,  81 

line,  103,  106,  190 

reactance,  105 
table  of,  105 
variation  with  frequency,  105 

voltage,  103 
Dynamos,  62 

alternating-current,  76 

Animas  Power  and  Water  Co. 's  plant, 
181 

cost  influenced  by  speed  of,  74 

direct-connected  unit,  74 
comparison  of  costs  of,  74 

direct -current,  71 

at  Drammen  (Norway)  plant,  188 
.     efficiency  of,  74,  77,  83,  88,  106,  174, 
188,  237 

inductor,  76 

of  Kern  River  (Cal.)  plant,  292 

losses  in,  83 

revolving  field,  77 

size  of,  for  given  service,  74,  86 

speed  regulation  of,  85 

at  Taylor's  Falls  (Minn.)  plant,  235 

at  Tofwehult  (Sweden)  plant,  157 

at  Trenton  Falls  (N.  Y.)  plant,  213 

"umbrella"  type,  262 

variation  of  voltage  in,  84,  237 

vertical,  62,  213 
thrust  of,  63 

voltage  of,  91,  92 

at  West  Buxton  (Maine)  plant,  173 

EARTH  DAMS,  26,  170,  177 

Effective  voltage,  107 

Efficiency  of  dynamos,  74,  77,  83,  88, 106 

of  Pelton  water-wheels,  67 

of  turbines,  59 
Electrical  equipment,  71 
Energy  losses  in  dynamos,  88 


INDEX 


313 


Excitation,  dynamo  field,  85,  91 

variation  in,  between  full  load  and 

no  load,  91 
Exciters,  73,  89,  90,  141,  143,  146,  184, 

187,   213,    222,   238,   292 

connections  of,  91 
current  for  lighting  from,   74,   296 
methods  of  driving,  89 
size  of,  90,  91,  292 
temperature,  rise  of,  91 
Exit  of  conductors  from    power-house, 
132,  297 

FALL,  measurement  of,  10 
Field  excitation,  85 
Flashboards,  170,  209,  275 
Float  for  measuring  stream-flow,  5,  7 
Floating  ice,  49 

Floods,  change  in  head  due  to,  60 
Floor  area  of  power-houses,  48 
Floors  of    power-houses.     See   Power- 
stations,  floors  of. 
Flow  of  streams,  2,  194,  216 

average  velocity  of,  6 

measurement  of,  2,  5,  6,  8,  9 

over  weirs,  table  of,  9 

per  square  mile  of  drainage  area,  194, 
216 

variation  in,   i,   194 
Flumes,  concrete,  273 

velocity  of  flow  in,  270 

wood,  176,  271,  276 
Fly-wheels  on  turbines,  86 
Forebays,  36,  50,  218,  222,  231,  275 
Foundations    of   dams,    2^,    166,    196, 
226 

of  power-houses,  48,  166,  282,  283 
Frame  dams.     See  Dams,  frame. 
Frazil  ice,  49,  50 
Frequency,  80,   147,   148,  149 

of  dynamos,  80 
Fuses,  150 

GATES,  HEAD.     See  Head-gates. 

sluice.     See  Sluice-gates. 

of  turbines,  53 

comparison  of,  55 
Gearing,  bevel,  63 
Generators.     See  Dynamos. 
Governors,    water-wheel.     See     Speed 

regulation  of  water-wheels. 
Gravity,  centres  of,  16 

dams.     See  Dams,  gravity. 
Great  Falls  plant  of  Southern  Power 

Co.,  193 

Ground  connections,  140,  149,  310 
Ground  detectors,  149 


HARD-DRAWN  COPPER  WIRE,  101,  190, 

301 

Head  gates,  197,  201,  220,  243,  267,  276, 
282 

motors  for,  202,  243,  282 
Head,  loss  of,  in  pipes,  35,  152 

net,  35 

reduction  in,  due  to  floods,  60 

suitable  for  impulse  turbines,  65 

for  pressure  turbines,  59 
Heat  liberated  in  conductors,  87 

in  dynamos,  87 
Height  of  power-houses,  48 
High-head  turbines,  212 
Horse-power,  71 

computation  of,  10,  12 
Hydraulic  developments:    (See  also  De- 
velopment.) 

comparison  of  methods,  12 

cost  of,  157 
Hydraulic  jx>wer,  computation  of,  2,  10 

storage  of,  3 
Hydraulic  thrust  bearings,  63 

ICE,  49,  1 66,  178,  222 

anchor,  215 

chutes,  220 

coating  on  wires,  120 

floating,  .19 

frazil,  49 

gorge,  1 66 

removal  of,  49 

surface,  49 
Impulse  turbines,  64 
Impulse  wheels,  46 

limiting  heads  for,  65 
Induction  motors,  power  factor  of,  71,  86 
Inductive  drop,  80 
Inductive  voltages  in  circuits,  86 
Inductor  dynamos,    76 
Insulation  of  armature  coils,  158 

breakdown  test  of,  158 

deterioration    of,    where   overheated, 

88 
Insulator  pins,  124 

deterioration  of,  125 

iron,  125,  249 

size  of,  125 

treatment  of,  125 
Insulators,  123,  247,  302 

cost  of,  124 

method  of  holding  to  iron  pins,  125, 
126,  248 

porcelain  vs.  glass,  123 

special  tension,  162 

strain,  248 


INDEX 


Insulators: 

suspension  type,  126 
advantages  of,  129 
methods  of  using,  127 
towers  for,  129 
tests  of,  124,  302 
Intermittent  power,  i,  2 

JET  impulse  wheels,  66 
speed  of,  66 

KERN  RIVER  PLANT,  263 
Kilo-volt  amperes,  87 
Kilo-watt,  71,  87 

LEAKAGE,  120 
Leaves,  removal  of,  49,  50 
Lightning,  135 

Lightning  arresters,  133,  136,  158,  188, 
297 

and  choke  coil  combined,  137 

choke  coils  for,  136,  241,  250,  297 

connections  for,  136,  140,  242,  250 

distribution  of,  along  lines,  139 

ground  connections  for,    140,   251 

horn  type,   137,   138,   139,   188,  192, 
249,  305  ^ 

knurled  cylinder  type,  136 

location  of,  136,  139,  192,  259,  305 

water-jet  type,  139 
Lightning  protection,  135,  139,  249,  259 

by  barbed  wire,  135,  140 
Lines:     (See   also   Conductors;  Trans- 
mission^lines ;  Wires.) 

apparent  energy  loss  in,  103 

drop  in,  102 

energy  loss  in,  103 

lightning    protection    for,    135,    138, 
139,  140,  188,  192,  242 

three-phase,  107 
Load,  inductive,  84 

non-inductive,  84 

variation  in,  85 

Log  chutes,  166,  167,  169,  231 
Long  pipes,  pressures  set  up  in,  152 
Losses  in  dynamos,  83 

in  lines,  102,  103,  106 

in  power,  10,  83,  106 

in  water-wheels,  59,  62,  74 

McCALL  FERRY  PLANT,  215 

Market  for  water-power,  4 

Masonry,  cyclopean,  30 

Masonry  dams,  29 

Maximum     power     obtainable     from 

hydraulic  developments,  3 
Measurement  of  streams,  2,  5,  6,  8,  10 


Middle  third  in  computations  of  sta- 
bility of  dams,  23 

Motors,  alternating-current,  72 
induction.     See  Induction  motors. 

NOZZLES,  deflecting,  67,  68,  180,  284 

needle,  67,  180,  284 

for  Pelton  wheels,  67 
Number  of  alternations  of  a  dynamo,  80 

of  poles  in  a  dynamo,  80 

OPEN  PENSTOCKS,  41,  42,  56,  57,  58 

PELTON  WATER  -WHEELS,  66,  1 8 1,  288 

effective  head  on,  67 

power  of,  67 

speed  of,  66,  288 
Penstocks,  55 

open,  41 

division  walls  of,  56 
superiority  of,  42 

steel,  40 

Piers  under  power-houses,  39,  167,  169 
Piles,  48 

Pins,  insulator.     See  Insulator  pins. 
Pipes,  32,  178,  202,  210 

anchoring  of,  on  inclines,  180 

cast  iron,  33 

computation  of  size  of,  34 

kinetic  energy  of  water  column  in,  69, 

I52 

loss  of  head  in,  34,  35,  152 

pressures  produced  in,  36,  69,  152 

riveting  of,  180 

stand.     See  Stand  pipes. 

steel,  33,  211,  279,  281 
cost  of,  34 
tapered,  178,  203 

velocity  of  water  in,  34 

warming  to  prevent  freezing,  178 

wood  stave,  33,  211 
Pole  lines,  122,  159,  175, 182,  190,  243 
Poles,  cost  of,  121 

dimensions  of,  176,  244,  245 

distance  between,  120,  190,  244 

height  of,  121 

iron,  192 

kinds  of,  121 

life  of,  121 

line,  1 20 

number  of,  in  a  dynamo,  80 

proportion's  of,  122 

setting  of,  122,  245 

and  towers  compared,  121 
Potential  drop  in  transmission  lines,  85 
Power,  available,  i 

computation  of,  2,  10 


INDEX 


315 


Power,  division  of,  among  units,  75 

electrical,  71 

horse-,  71 

in  an  electric  circuit,  71 

intermittent,   i,   2 

market  for,  4 

maximum  obtainable,  2,  3 
Power  factor,  71,  86,  91 

of  arc  lamps,  71 

definition  of,  86 

of  induction  motors,  71 
Power-houses.     See  Power  stations. 
Power  stations,  bulkhead  of,  44 

floor  area  of,  48 

floors  of,  169 

location  of,  34,  44 

materials  used  in  construction  of,  47 

piers  under,  39,  167,  169,  206 

roofs  of,  48,  169,  207,  284 

storage,  3,  n,  12 

types  of,  38 

Pressure  turbines,  51,  57 
Pressures  against  dams,  18 

on  turbine  wheels,  57 

set  up  in  pipes,  36,  69,  152 

to  overturn  dams,  20,  23 
Protection  against  trash.     See  Booms; 
Racks;  Trash. 

against  ice.     See  Ice. 

QUARTER-TURNS,  58 

RACKS,  36,  50,  168,  178,  196,  198,  200, 

218,  231,  265,  275,  276 
Reactance,  105 

Reactance  drops,  table  of,  105 
Register  gates,  54 
Regulation  of  dynamos,  84 
speed,  85 
voltage,  91 

of  transmission  line,  85 

of  turbine  speed,  57,  67,  180,  200 
Regulators,  voltage,  85,  96 
Relief  pipe,  178 
Relief  valves,  68,  212 
Reservoirs,  n 

drop  in  level  allowable,  n 
Resonance,  86,  135 
Revolving  field  dynamos,  77 
Rheostats,  91 
Roofs  for  power-houses,  48,   169,  207, 

284 

Rope-driven  units,  75 
Rotary  converters,  81,  83,  85,  258 

SAND,  action  of,  on  water-wheels,  49 
removal  of,  49,  184 


Sand  trap,  184 

Settling  basins,  49,  50 

Shear  legs,  49 

Shock  from  transformers,  93 

Single-phase  systems,  103,  112 

Sluice  gates,  169,  183,  184,  198,  208,  275 

Sluice  ways,  166,  169,  231,  267 

Southern     Power     Co.'s     Great     Falls 

plant,  193 

Spans,  length  of,  for  wires,  720 
Speed  control  of  water-wheels,   57,   67 

1 80,  206,  234,  290 
Speed  governors,  68 
Speed  regulation  of  dynamos,  85 
Speed  of  water-wheels,  52,  57,  60,  66 
Spillway  of  dams,  25,  35 
Spouting  velocity,  52 
Standard  wires,  100 
Stand  pipes,  37,  178,  211 
Static  charge,  protection  against,  158 
Static  discharge,  93,   135,  240 
Steam  plants,  auxiliary.     See  Auxiliary 

steam  plants. 

Steel  towers.     See  Towers,  steel. 
Stop  logs,  35 
Storage,  hydraulic,  3,  n 

amount  of,  1 1 
Stream  flow,  average  velocity  of,  6 

computation  of,  194,  216 

equalization  of,    3 

influence  of  forest  growths  on,  6 

measurement  of,  4,  8 
Streams,  cross-section  of,  6 

effect  of  forest  growths  on  flow  of,  i 

flow  of,  i,  2,  194,  216 

measurement  of,  2 

Substations,  191,  253,  259,  304,  307 
Surface  ice,  49 

Surging  on  transmission  lines,  135 
Switchboards,  141,  143,  150,  189,  213 

connections  of,  49,  257 

cost  of,  92 

gallery  for,  49,  284 

general  rules  in  design  of,  151 

iron  framework  for,   143,  144 

location  of,  49 

panels  of,  143 

wall  braces  for,  150 

at  Drammen,  Norway,  189 

Kern  River  plant,  California,  295 

Taylor's  Falls  (Minn.),  242,  254 

Trenton  Falls  (New  York),  213 

West  Buxton  (Maine),  174 
Switches,  automatic,  141,  174,  241 

chambers  for,  141,  295 

generator  field,  142 

high-tension,  49,  141,  144,  149,  305 


3i6 


INDEX 


Switches,  oil,  141,  174,  189,  240,  241, 
294,  295,  305 

knife,  142 

three-phase,  142 
Switching    and    controlling   apparatus, 

141,  239 
Synchronous  machinerv,  85 

speed  of,  relative  to  dynamo  speed,  85 
Synchroscope,  146,  149 
Systems,  comparison  of  Y  and  A  con- 
nections, 99 

Delta-connected,  97 

resultant  mesh-connected,  98 

star-connected,  97 

voltage   of.     See  Voltage  of  systems. 

TABLE  of  cost  of  riveted  steel  pipe,  34 

of  current    allowable  in  bare  copper 
wires,  103 

of  dimensions  and   weights  of  bare 
copper  wires,  IOT 

of  flow  over  rectangular  weirs,  9 

of  reactance  drop  per   1000  feet  of 
circuit,  105 

of  resistances  of  bare  copper  wire,  101 

of  thickness  of  core  walls  for  earth 
dams,  27 

of  weights  of  bare  copper  wire,  101 
Taylor's   Falls — Minneapolis    develop- 
ment, 230 
Telephone     circuits     on     transmission 

pole  lines,  162,  175,  190,  243,  300,  304 
Temperature  rise  in  electrical  apparatus, 

87,  88,  91 
Three-phase  systems,  80,  107,  116,  148 

balancing  of,  148 

computation  of,  107,  113 

drop  in,  107,  in,  113 

effective  voltage  of,  108 

reactance    of,    107 
Thrust  bearings,  63,  222 
Thrust  on  turbine  shafts,  61 
Timber  dams,  27 
Towers,  steel,  120,  246,  299 

cost  of,  121 

spacing  of,  303 
Transformers,  advantages  of  large,  96 

air-cooled,  94,  213 

capacity  of,  96 

cars  and  tracks  for,  93,  190,  233,  239 

cases  of  grounded,  96 

chambers  for,  93,  233,  238 

efficiency  of,  96 

instrument,  147,  148,  149,  150 

location  of,  73,  93 

methods  of  cooling,  94 
of  connecting,  97,  293,  294 


Transformers,    number  required   in   3- 

phase  systems,  96 
oil-cooled,  93,  94,   237,   293,  308 
oil-insulated,  94,  95,  174,  293,  305 
overload  on,  99 
regulation  of,  96 
rollers  under,  93,  190,  233,  254 
secondary  of  grounded,  97 
separate  building  for,  94,  208 
siphon  for  cooling,  95 
spare,  99 

step-down,  93,  106,  107 
step-up,  92,  106,  107 
water-cooled,  94,  174,  237,   254,  305 
Transmission  conductors,  100.     See  also 

Conductors;  Wires 
electrical  problems  of,  100 
mechanical  problems  of,  100 
Transmission  lines,  92,   146,   159,   175, 

182,  190,  213,  243,  297,  301 
drop  in,  102 
energy  loss  in,  103 
exit  of,  from  power-house,  132 
inductive  drop  in,  81 
leakage  on,  120 
poles  for,  1 20.     See  also  Poles;  Pole 

lines. 
Transmission   systems,    Animas  Power 

and  Water  Co.  (Col.),  176 
Drammen  (Norway),  183 
Great  Falls  (S.  C.),  193 
McCall  Ferry  (Pa).,  215 
Taylor's  Falls  (Minn.),  229 
three-phase.     See  Three-phase    Sys- 
tems. 

Tofwehult-Westerwik  (Sweden),   157 
Trenton  Falls  (N.  Y.),  203 
voltage  of.     See  Voltage  of  systems. 
Transposition  of  circuits,  116,  162,  190, 

246 

Trash,  protection  against,  35,  49,  167 
Trash  racks.     See  Racks. 
Trees    and     shrubbery,    effect    of,    on 

stream  flow,  3 
Trenton  Falls  plant,  208 
Turbines,  51,  59 

arrangements  of,   to  compensate  for 

variations  in  head  on,  60 
belt-connected,  46 
comparison  of  impulse  and  pressure 

types,  65 
of  central  draft  chest  and  double 

draught-tube  units,  58 
of  costs  of  single  and  double  units, 

74 

direct-connected,  40 
division  of  power  between,  57 


INDEX 


317 


Turbines,  double  units,  74 

drainage  valves  in  case  of,  203 

efficiency  of,  59,  62,  74,  157,  187,  204, 
205 

fly-wheels  on,  86,  186,  187 
gates  of,  53 

high-head,  212,  213 

horizontal,  52,  5=5 

impulse,  64 

inward-flow,  51 

location  of,  39,  40,  43,  44,  46,  52 

low-speed,  46 

methcxls  of  setting,  55 

outward-flow,    51 

parallel-flow,  51 

power  of,  74 

pressures  in,  57 

set  in  open  penstocks,  41 

shell-encased,  40 

size  of,  1 06,  iii,  204 

of  Southern  Power  Co.'s  Great  Falls 
plant,   203 

speed  of,  52,  60 

speed  of  gate  opening  allowable,  69 

speed    regulation  of,  57,  68,  69,  180 
186,   187,   234 

tandem -coupled,  46,  222 

of  Trenton  Falls  plant,  213 

variation  in  head  on,  60 

vertical,  52,  55,  62,  63,  213,  222 
Turns,  quarter,  58 

UNDERGROUND  CABLES,  191,  192,  259, 

260 
Units,  belt-driven,  75 

comparison  of  costs  of,  74 

direct-connected,  74 

efficiency  of,  74 

number  of,  for  a  given  output,  75 

rope-driven,  75 

VALUE  of  a  water-power,  4 
Valves,  by-pass,  180 

relief,  68 

Variation  in  stream  flow,  i 
Vegetable  growths,  effect  of,  2 
Velocity  of  flow  in  draught  tubes,  59 

in  feed  pipes,  34 

in  flumes,  270 
Velocity  of  streams,  6 


Velocity,  spouting,  52 

Volt,  71 

Voltage  drop  in  lines,  85,  103 

regulators,  85,  96 
Voltage,  of  dynamos,  91,  92 

effective,  in  three-phase  systems,  108 
of  systems,  73,  80,  92,  93,   159,   162, 
163,   174,   175,   181,   184,   i"88,   190 
191,  213,  233,  237,  239,  243,  253, 
264,  293,  305,  307 
Voltmeters,  connections  of,   147 

WATER-TETS,  protection  against  erosion 

of,  46 

Water-hammer,  prevention  of,  36 
Water-power,  value  of,  4 
Water-wheels,  51 

capacity  of,  74 

governors     for.      Sec    Water-wheels, 
speed  regulation  of 

height  alx>vc  tail  water  of,  47,  282 

impulse,  46 

location  of,  39,  40,  43,  44,  46,  47 

speed  regulation  of,  57,  68,  180,  206, 

234,  288,  290 
Wattmeters,  148 
Watts,  71,  87 
Weirs,  8 

table  of  flow  over,  9 
Wicket  gates,  53 
\Vires,  aluminum,  114,  162 

arrangement  of,  115,  175,  190,   244, 
258 

barbed,  for  lightning  protection,  135, 
140 

distance  apart  of,  119,  175,  183,  244, 
258,  299,  301 

exit  of,  from  power-houses,  132,  297 

hard -drawn  copper,  101 

ice-coating  on,  120 

length  of  spans  of,  120,  160,  303 

required  for  transmission,  73 

sag  in,  i  iS 

standard,  table  of  dimensions,  weights, 
and  resistances,  100 

steel,  for  long  spans,  160 

swinging  of  suspended,  131 

telephone,  162,  175,  190,  243,  258 

transposition  of,   116,   162,   190,   246 

underground,  191,  192,  259,  260 


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